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Diabetes insipidus is a disorder characterized by excretion of large amounts of hypotonic urine. Four entities have to be differentiated: central diabetes insipidus resulting from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, nephrogenic diabetes insipidus resulting from resistance to AVP in the kidneys, gestational diabetes insipidus resulting from an increase in placental vasopressinase and finally primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Distinguishing between the different types of diabetes insipidus can be challenging. A detailed medical history, physical examination and imaging studies are needed to detect the aetiology of diabetes insipidus. Differentiation between the various forms of hypotonic polyuria is then done by the classical water deprivation test or the more recently developed hypertonic saline or arginine stimulation together with copeptin (or AVP) measurement. In patients with idiopathic central DI, a close follow-up is needed since central DI can be the first sign of an underlying pathology. Treatment of diabetes insipidus or primary polydipsia depends on the underlying aetiology and differs in central diabetes insipidus, nephrogenic diabetes insipidus and primary polydipsia. This review will discuss issues and newest developments in diagnosis, differential diagnosis and treatment, with a focus on central diabetes insipidus., (© 2021 The Association for the Publication of the Journal of Internal Medicine.)

We characterized mouse blood pressure and ion transport in the setting of commonly used rodent diets that drive K + intake to the extremes of deficiency and excess. Male 129S2/Sv mice were fed either K + -deficient, control, high-K + basic, or high-KCl diets for 10 days. Mice maintained on a K + -deficient diet exhibited no change in blood pressure, whereas K + -loaded mice developed an ~10-mmHg blood pressure increase. Following challenge with NaCl, K + -deficient mice developed a salt-sensitive 8 mmHg increase in blood pressure, whereas blood pressure was unchanged in mice fed high-K + diets. Notably, 10 days of K + depletion induced diabetes insipidus and upregulation of phosphorylated NaCl cotransporter, proximal Na + transporters, and pendrin, likely contributing to the K + -deficient NaCl sensitivity. While the anionic content with high-K + diets had distinct effects on transporter expression along the nephron, both K + basic and KCl diets had a similar increase in blood pressure. The blood pressure elevation on high-K + diets correlated with increased Na + -K + -2Cl - cotransporter and γ-epithelial Na + channel expression and increased urinary response to furosemide and amiloride. We conclude that the dietary K + maneuvers used here did not recapitulate the inverse effects of K + on blood pressure observed in human epidemiological studies. This may be due to the extreme degree of K + stress, the low-Na + -to-K + ratio, the duration of treatment, and the development of other coinciding events, such as diabetes insipidus. These factors must be taken into consideration when studying the physiological effects of dietary K + loading and depletion.

Dysregulated arousal often accompanies neurodevelopmental disorders such as attention deficit hyperactivity disorder and autism spectrum disorder. Recently, we have found that adolescent homozygous Brattleboro (Hom) rats, which contain a mutation in the arginine vasopressin (AVP) gene, exhibit lower behavioral arousal than their heterozygous (Het) littermates in the open field test. This hypoaroused phenotype could be due to loss of AVP in magnocellular cells that supply AVP to the peripheral circulation and project to limbic structures or parvocellular cells that regulate the stress axis and other central targets. Alternatively, hypoarousal could be a side effect of diabetes insipidus - polydipsia and polyuria seen in Hom rats due to loss of AVP facilitation of water reabsorption in the kidney. We developed a viral-rescue approach to "cure" magnocellular AVP cells of their Brattleboro mutation. Infusion of a recombinant adeno-associated virus (rAAV) containing a functional Avp gene and promoter (rAAV-AVP) rescued AVP within magnocellular cells and fiber projections of the paraventricular nucleus of the hypothalamus (PVN) of male and female adolescent Hom rats. Furthermore, water intake was markedly reduced, ameliorating the symptoms of diabetes insipidus. In contrast, open field activity was unaffected. These findings indicate that the hyporaoused phenotype of adolescent Hom rats is not due to the loss of AVP function in magnocellular cells or a side effect of diabetes insipidus, but favors the hypothesis that central, parvocellular AVP mechanisms underlie the regulation of arousal during adolescence.

Although hyperemesis gravidarum (HG), an extreme form of morning sickness, is a common complication during pregnancy, HG associated simultaneous onset of rhabdomyolysis and diabetes insipidus due to electrolyte abnormalities are rare. A 34-year-old woman with severe HG at 17 weeks of gestation complicated with appetite loss, weight reduction by 17 kg, general fatigue, myalgia, weakness and polyuria was identified to have simultaneous hypophosphatemia (1.6 mg/dL) and hypokalemia (2.0 mEq/L). Appetite recovery and the improvement of the hypophosphatemia (3.2 mg/dL) were observed prior to the first visit to our department. At the admission, she presented polyuria around 7,000~8,000 mL/day with impaired concentrating activity (U-Osm 185 mOsm/L), and abnormal creatine kinase elevation (4,505 U/L). The electrolyte disturbances and physio-metabolic abnormalities in undernourished state due to HG let us diagnose this case as refeeding syndrome (RFS). In this case, abnormal loss by vomiting, insufficient intake and previous inappropriate fluid infusion as well as the development of RFS may accelerate the severity of hypokalemia due to HG. Thus, as her abnormalities were considered as results of rhabdomyolysis and diabetes insipidus due to severe HG associated hypokalemia based on RFS, oral supplementation of potassium chloride was initiated. After 6 days of potassium supplementation, her symptoms and biochemical abnormalities were completely resolved. Severe HG followed by RFS can be causes of electrolyte abnormalities and subsequent complications, including rhabdomyolysis and renal diabetes insipidus. Appropriate diagnosis and prompt interventions including adequate nutrition are necessary to prevent electrolyte imbalance induced cardiac, neuromuscular and/or renal complications.

The antidiuretic hormone vasopressin (VP) is produced by the hypothalamus and is stored and secreted from the posterior pituitary. VP acts via VP type 2 receptors (V2Rs) on the basolateral membrane of principal cells of the collecting duct (CD) to regulate fluid permeability. The VP-evoked endocrine pathway is essential in determining urine concentrating capability. For example, a defect in any component of the VP signaling pathway can result in polyuria, polydipsia, and hypotonic urine, collectively termed diabetes insipidus (DI). A lack of VP production precipitates central diabetes insipidus (CDI), which can be managed effectively by VP supplementation. A majority of cases of nephrogenic diabetes insipidus (NDI) result from V2R mutations that impair receptor sensitivity. No specific therapy is currently available for management of NDI. Evidence is evolving that (pro)renin receptor (PRR), a newly identified member of the renin-angiotensin system, is capable of regulating VP production and action. As such, PRR should be considered strongly as a therapeutic target for treating CDI and NDI. The current review will summarize recent advances in understanding the physiology of renal and central PRR as it relates to the two types of DI.

The paraventricular nucleus of the hypothalamus (PVH), located in the ventral diencephalon adjacent to the third ventricle, is a highly conserved brain region present in species from zebrafish to humans. The PVH is composed of three main types of neurons, magnocellular, parvocellular, and long-projecting neurons, which play imperative roles in the regulation of energy balance and various endocrinological activities. In this review, we focus mainly on recent findings about the early development of the hypothalamus and the PVH, the functions of the PVH in the modulation of energy homeostasis and in the hypothalamus-pituitary system, and human diseases associated with the PVH, such as obesity, short stature, hypertension, and diabetes insipidus. Thus, the investigations of the PVH will benefit not only understanding of the development of the central nervous system but also the etiology of and therapy for human diseases.

Both microscopic and endoscopic transsphenoidal surgery are effective approaches for nonfunctioning pituitary adenomas. The issue on the comparison of their efficacy and safety remains inconsistent. A thorough search of the literatures (PubMed, EMBASE, MEDLINE) were performed up to March 2017. Studies reporting outcomes of microscopic or endoscopic transsphenoidal surgery on nonfunctioning pituitary adenomas were included. A meta-analysis was performed focusing on the early stage and long term outcomes. The final search yielded 19 eligible studies enrolling 3847 patients, 389 of them underwent microscopic approach and 3458 of them with endoscopic approach. As to the early stage outcomes, the rate of gross tumor resection was significantly higher in the endoscopic group than that in microscopic group (73% versus 60%, P < 0.001). Meanwhile, endoscopic approach showed priority over microscopy on postoperative hypopituitarism (63% versus 65%, P < 0.001) and CSF leakage (3% versus 7%, P < 0.001). For the long term outcomes, the rate of visual improvement was significant higher in the endoscopic group than that in microscopic group (77% versus 50%, P < 0.001). However, there was no significant difference between the groups regarding the rate of permanent diabetic insipidus and meningitis. The endoscopic approach may be associated with higher rate of gross tumor movement and lower risk of postoperatively complications for treating nonfunctioning pituitary adenoma, when compared with microscopic approach. However, the confidence was shorted due to limited high quality evidence (largely randomized and controlled studies)., (© 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

Background: Gestational diabetes insipidus (GDI) is a rare endocrine complication during pregnancy that is associated with vasopressinase overproduction from the placenta. Although increased vasopressinase is associated with placental volume, the regulation of placental growth in the later stage of pregnancy is not well known., Case Presentation: A 16-year-old pregnant woman was urgently transferred to our hospital because of threatened premature labor when the Kumamoto earthquakes hit the area where she lived. During her hospitalization, she complained of gradually increasing symptoms of polyuria and polydipsia. The serum level of arginine vasopressin (AVP) was 1.7 pg/mL, which is inconsistent with central DI. The challenge of diagnostic treatment using oral 1-deamino-8-D-AVP (DDAVP) successfully controlled her urine and allowed for normal delivery. DDAVP tablets were not necessary to control her polyuria thereafter. Based on these observations, clinical diagnosis of GDI was confirmed. Pathophysiological analyses revealed that vasopressinase expression was more abundant in the GDI patient's syncytiotrophoblast in placenta compared with that in a control subject. Serum vasopressinase was also observed during gestation and disappeared soon after delivery. Vasopressinase is reportedly identical to oxytocinase or insulin regulated aminopeptidase (IRAP), which is an abundant cargo protein associated with the glucose transporter 4 (GLUT4) storage vesicle. Interestingly, the expression and subcellular localization of GLUT4 appeared to occur in a vasopressinase (IRAP)-dependent manner., Conclusion: Because placental volume may be associated with vasopressinase overproduction in GDI, vasopressinase (IRAP)/GLUT4 association appears to contribute to the growth of placenta in this case.

Background and Aims: Retrospective studies of TBI have found a neuroendocrine dysfunction following traumatic brain injury in 23 to 60% of adults and 15 to 21% of children. Our aims were to determine the prevalence of hypothalamo-hypophyseal dysfunction in children following brain injury, assess its relationship to the type of injury and the course of the acute post-traumatic phase., Patients and Methods: Body development (growth, pubertal development, and skeletal maturity) were evaluated in 58 patients (21 girls) after a brain injury rated 3 to 12 on the Glasgow Coma Scale (GCS). The patients underwent standard endocrine tests - TSH, fT4, IGF-1, PRL, morning cortisol, FSH, LH, and testosterone in boys and estradiol in girls - in the early post-traumatic period (2 to 14 days; T0) and at 3, 6, and 12 months after the injury (T3, T6, and T12). Dynamic tests were carried out in patients with abnormalities in their clinical examination and/or laboratory results. An MRI was performed on all patients at T12., Results: The median age at the time of injury was 11.3 (0.5 to 18.7) years. Of the 58 patients, 23 had GCS < 8, corresponding to severe brain injury. At T0, diabetes insipidus (DI) was diagnosed in 12 patients, and the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was found in 4 patients. Frequent hormonal changes simulated central hypothyroidism (in 45% of patients) and hypogonadotropic hypogonadism (in 25% of adolescents who were already pubertal at the time of injury > Tanner II). Examination at T3 (n = 58) confirmed a combined pituitary hormone deficiency in two boys and DI in another one. At T6 (n = 49), hormonal dysfunctions were diagnosed in two boys (precocious puberty and growth hormone deficiency). At T12 (n = 39), a new endocrine dysfunction was diagnosed in five patients (growth hormone deficiency in two, hypogonadotropic hypogonadism in two, and in one patient, already diagnosed with a growth hormone deficiency, central hypothyroidism, as well). Brain MRI revealed an empty sella in two patients with growth hormone deficiency. Patients with GCS < 8 had more symptoms of SIADH or DI in the early post-traumatic period 11/23 vs. patients with GCS of 8 to 13 (4/35), and more frequent hormonal disorder (6/23) than individuals with moderate trauma (3/35), P = 0.0135. The incidence of endocrine dysfunction at T0 significantly correlated with the severity of injury (P = 0.05), but it was not an indicator for the development of a late hormonal disorder., Conclusion: Within a year after injury, a hormonal disorder was found in 17.6% of the patients. Neuroendocrine dysfunction as a late consequence of craniocerebral trauma in children and adolescents was less frequent than in adults. Risk factors for its development are the gravity of the injury, brain scan pathology, and possibly the development of DI, SIADH, or CSWS in the acute post-traumatic phase.

The clinical picture of IgG4-related disease (IgG4-RD) is diverse because various organs can be affected. We describe the case of a 56-year-old man with acute renal failure and tuberoinfundibular hypophysitis due to IgG4-RD. Steroid therapy lowered the serum IgG4 level and ameliorated renal dysfunction, bilateral hydronephrosis and retroperitoneal fibrosis. However, polyuria from post-obstructive diuresis and unmasked central diabetes insipidus ensued. The patient's polyuria continued despite the administration of a therapeutic dose of glucocorticoid; the patient's pituitary swelling and anterior pituitary dysfunction were partially ameliorated. The pituitary swelling recurred seven months later. In patients with IgG4-RD, the manifestation of polyuria after steroid therapy should prompt suspicion of post-obstructive diuresis and the unmasking of central diabetes insipidus.

Background: Diabetes insipidus (DI) is a rare disease in humans and animals, which is caused by the lack of production, malfunction or dysfunction of the distal nephron to the antidiuretic effect of the antidiuretic hormone (ADH). Diagnosis requires a thorough medical history, clinical examination and further laboratory confirmation. This case report describes the appearance of DI in five Duroc boars in Switzerland., Case Presentation: Two purebred intact Duroc boars at the age of 8 months and 1.5 years, respectively, with a history of polyuric and polydipsic symptoms had been referred to the Swine Clinic in Berne. Based on the case history, the results of clinical examination and the analysis of blood and urine, a tentative diagnosis of DI was concluded. Finally, the diagnosis was confirmed by findings from a modified water deprivation test, macroscopic examinations and histopathology. Following the diagnosis, three genes known to be involved in inherited DI in humans were analyzed in order to explore a possible genetic background of the affected boars., Conclusion: The etiology of DI in pigs is supposed to be the same as in humans, although this disease has never been described in pigs before. Thus, although occurring only on rare occasions, DI should be considered as a differential diagnosis in pigs with polyuria and polydipsia. It seems that a modified water deprivation test may be a helpful tool for confirming a diagnosis in pigs. Since hereditary forms of DI have been described in humans, the occurrence of DI in pigs should be considered in breeding programs although we were not able to identify a disease associated mutation.

Alterations in water homeostasis can disturb cell size and function. Although most cells can internally regulate cell volume in response to osmolar stress, neurons are particularly at risk given a combination of complex cell function and space restriction within the calvarium. Thus, regulating water balance is fundamental to survival. Through specialized neuronal "osmoreceptors" that sense changes in plasma osmolality, vasopressin release and thirst are titrated in order to achieve water balance. Fine-tuning of water absorption occurs along the collecting duct, and depends on unique structural modifications of renal tubular epithelium that confer a wide range of water permeability. In this article, we review the mechanisms that ensure water homeostasis as well as the fundamentals of disorders of water balance., (Copyright © 2015 by the American Society of Nephrology.)

A patient assessed by heart rate variability (HRV) methodology, beginning just after the completion of brain death (BD) diagnosis, showed remaining very low frequency (VLF) waves for approximately 10 min. A time-varying spectral analysis showed that during the first 550 s, a significant power spectral density remained in the high-frequency (HF), low-frequency (LF) and VLF bands. From 550 to 675 s, the HF oscillations totally vanished, and a marked progressive decay of the LF and VLF power density occurred. After 700 s the VLF undulations stopped and remaining small amplitude oscillations at 0.2 Hz coincided with the ventilator frequency. The VLF oscillations recorded in our case might be related to residual sympathetic vasomotor activity that progressively disappeared due to the extension of necrosis affecting the nervous centres of the lower part of the medulla and the first 2-3 cervical spine segments., (2015 BMJ Publishing Group Ltd.)

Hyponatremia is a common and potentially serious complication of transsphenoidal surgery (TSS). Since September 2009, we have implemented moderate water intake restriction (< 2500 mL/day) after TSS in an attempt to prevent this complication. The aim of this study was to investigate the efficacy of a combination of moderate restriction of water intake plus antidiuretic hormone (arginine vasopressin [AVP]) replacement therapy in patients with diabetes insipidus (DI) for reducing the incidence of delayed hyponatremia after TSS. Patients treated from September 2005 to August 2009 were allowed to drink water freely after surgery (the control group), while patients treated from September 2009 to June 2012 were restricted to less than 2500 mL water per day (the water restriction group). To reduce the occurrence of hypernatremia, AVP replacement therapy was provided immediately after the development of DI. We retrospectively analyzed the incidence of hyponatremia, DI, and hypernatremia in patients following TSS. Hyponatremia incidence was significantly lower in the water restriction group (P = 0.017); however, there were no significant differences in DI incidence and hypernatremia incidence between the 2 groups. Under DI control with AVP replacement therapy, the water restriction group showed no significant difference in the daily self-rated thirst level for the patients with and without DI. Moderate water intake restriction in addition to AVP replacement therapy significantly decreases the incidence of hyponatremia without patient discomfort (extreme thirst) and other complications. However, further studies are required to determine the most effective amount of water and the optimal duration of postoperative water restriction.

Background: We are describing an unusual case of severe hyperglycemia and hypernatremia, resistant to treatment., Case Presentation: A thirty year old female with adenocarcinoma of rectum was admitted with increasing lethargy, headache and drowsiness. She deteriorated rapidly and had cardiac arrest, following which she remained comatose. Her initial serum glucose and sodium were normal, but after receiving dexamethasone and mannitol, the serum glucose progressively increased to 54.7 mmol/L and sodium to 175 mmol/L, despite receiving very high dose of intravenous (IV) insulin infusion. She was evaluated for diabetes insipidus because of continued polyuria even after correction of hyperglycemia. Her serum osmolality was 337 mmol/kg, and urine osmolality was 141 mmol/kg which rose to 382 mmol/kg, after receiving 4 mcg of IV Desmopressin., Conclusion: Our patient developed central diabetes insipidus post cardiac arrest and severe dehydration because of diabetes insipidus. Stress of critical illness, dehydration, dexamethasone and IV dextrose infusion were likely responsible for this degree of severe and resistant to treatment hyperglycemia.

Context: Pituitary stalk lesions have various etiologies, often not clinically apparent. Pathological samples from these lesions are rarely obtained, because of the critical location and function of the hypophyseal stalk., Objectives: The purpose of this study was to characterize the etiological spectrum of pituitary stalk lesions seen at Mayo Clinic Rochester over 20 years and to determine whether specific magnetic resonance imaging (MRI) characteristics could provide clinician guidance with regard to the etiology of infundibular lesions., Design: A retrospective review of patients with pituitary stalk lesions seen at Mayo Clinic Rochester between 1987 and 2006 was conducted. Demographic, clinical presentation, imaging, laboratory, operative, and pathology data were reviewed and are reported using descriptive statistics., Results: Of the 152 pituitary stalk lesions included, 49 (32%) were neoplastic, 30 (20%) were inflammatory, 13 (9%) were congenital anomalies, and 60 (39%) were of unclear etiology. Diabetes insipidus was diagnosed in 43 (28%) of the 152 patients, and 49 (32%) patients had at least one anterior pituitary hormone deficit. Secondary hypogonadism was the most common endocrine deficiency. Eleven of 13 congenital lesions were round in appearance and 5 of 7 patients with neurosarcoidosis confirmed by pathology had a uniformly thickened pituitary stalk on MRI. There were no statistically significant correlations between hypopituitarism and the pattern of enhancement or size of the lesion., Conclusions: Findings on MRI remain key in guiding the diagnosis of pituitary stalk lesions, particularly when used in conjunction with other clinical clues. There are no good imaging predictors for hypopituitarism, making clinical evaluation of all patients with pituitary stalk lesions crucial.

Many complications have been reported after cardiopulmonary bypass. A common physiologic change during the early postoperative period after cardiopulmonary bypass is increased diuresis. In patients whose urine output is increased, postoperative diabetes insipidus can develop, although reports of this are rare. We present the cases of 2 patients who underwent on-pump coronary artery bypass grafting (with cardiopulmonary bypass). Each was diagnosed with diabetes insipidus postoperatively: a 54-year-old man on the 3rd day, and a 66-year-old man on the 4th day. Each patient recovered from the condition after 6 hours of intranasal therapy with synthetic vasopressin (antidiuretic hormone). The diagnosis of diabetes insipidus should be considered in patients who produce excessive urine early after cardiac surgery in which cardiopulmonary bypass has been used.

Recent discoveries have shed new light on the understanding of water metabolism: (1.) in addition to hypothalamic osmoreceptor cells expressing a TRPV1 variant, there are peripheral TRPV4 receptors sensing tonicity in the portal vein and changing central vasopressin secretion and peripheral autonomic activity; (2.) the central osmoregulatory gain of angiotensin action participates in the non-osmotic release of vasopressin induced by hypovolaemia; (3.) prostaglandins EP2 receptors on principal cells of the collecting ducts positively regulate urine concentration mechanisms. These new developments are important clinically for the understanding of hereditary polyuric states. We recommend sequencing of the nephrogenic diabetes insipidus genes in all affected patients. This genomic information is key to the routine care of patients with congenital polyuria and, as in other genetic diseases, reduces health costs and confers psychological benefits on patients and families.

To investigate the underlying causes for aldose reductase deficiency-induced diabetes insipidus, we carried out studies with three genotypic groups of mice. These included wild-type mice, knockout mice, and a newly created bitransgenic line that was homozygous for both the aldose reductase null mutation and an aldose reductase knockin transgene driven by the kidney-specific cadherin promoter to direct transgene expression in the collecting tubule epithelial cells. We found that from early renal developmental stages onward, urine osmolality did not exceed 1,000 mosmol/kgH2O in aldose reductase-deficient mice. The functional defects were correlated with significant renal cellular and structural abnormalities that included cell shrinkage, apoptosis, disorganized tubular and vascular structures, and segmental atrophy. In contrast, the transgenic aldose reductase expression in the bitransgenic mice largely but incompletely rescued urine concentrating capacity and significantly improved renal cell survival, cellular morphology, and renal structures. Together, these results suggest that aldose reductase not only plays important roles in osmoregulation and medullary cell survival but may also be essential for the full maturation of the urine concentrating mechanism.

The mechanism of spontaneous resolution of diabetes insipidus (DI) was investigated after surgery for large craniopharyngioma. Twenty-two adult patients (mean age 48.9 years old), who underwent surgery via the anterior interhemispheric trans-lamina terminalis approach, were divided into three groups: Group I, the entire pituitary stalk was preserved (n = 2); Group II, the stalk was dissected distally from the tumor but ultimately sacrificed (n = 9); Group III, the stalk was not identified and was sacrificed (n = 11). All patients were discharged without neurological deficits 1 month after surgery. Four patients underwent gamma-knife treatment for residual tumor or recurrence. Postoperative endocrinological functions were normal in Group I, and no replacement therapy was required. Hormonal replacement for pan-hypopituitarism and DI was necessary in Groups II and III (mean follow-up period 5.9 years). DI resolved at 2.7 +/- 1.3 years after surgery in four patients in Group II, and a hypertonic saline infusion test revealed production of small amounts of intrinsic antidiuretic hormone (ADH). Urine osmolarity was high in the morning, and a significant increase in urinary osmolarity was noted after Pitressin injection. These results indicate induction of hypersensitivity of the distal renal tubules to small amounts of intrinsic ADH, resulting in decreased urinary output. Recovery from DI can be expected, despite permanent impairment of anterior pituitary function, if the pituitary stalk is dissected as distally as possible.

Diabetes insipidus, characterized by excretion of copious volumes of dilute urine, can be life-threatening if not properly diagnosed and managed. It can be caused by two fundamentally different defects: inadequate or impaired secretion of antidiuretic hormone (ADH) from the posterior pituitary gland (neurogenic or central diabetes insipidus) or impaired or insufficient renal response to ADH (nephrogenic diabetes insipidus). The distinction is essential for effective treatment.

Background: The antidiuretic effect of oxytocin in humans is controversial. Urinary excretion of aquaporin-2 (AQP2) can be used as an index of the action of vasopressin on the kidney. We investigated whether exogenous oxytocin affects urinary concentration and urinary AQP2 excretion in human beings., Methods: Oxytocin was administered intravenously at a rate of 20 mU/min in 10 healthy volunteers, seven patients with central diabetes insipidus (CDI) and three patients with nephrogenic diabetes insipidus (NDI). On the next day, 2 micro g of 1-desamino-8-d-arginine vasopressin (dDAVP) was injected subcutaneously. Two-hour urine was collected before and after the administration of oxytocin and dDAVP, and urinary AQP2 was measured semi-quantitatively by western analysis., Results: Urine volume and free water clearance were decreased, and urine osmolality was increased by the administration of oxytocin or dDAVP in the normal volunteers and CDI patients. Urinary AQP2 excretion was increased by oxytocin infusion in the normal volunteers (from 34+/-12 to 326+/-120 densitometry unit (DU)/2 h) and in the CDI group (from 8+/-2 to 227+/-92 DU/2 h) (P<0.05), but not in the NDI group. dDAVP also had a similar but more potent effect on the urinary excretion of AQP2 in the normal and CDI groups., Conclusions: Oxytocin has an antidiuretic effect and increases the urinary excretion of AQP2 in humans whose urinary concentration mechanism is preserved. These results suggest that AQP2 might have a regulatory role in the antidiuretic action of oxytocin in humans.

Chronic consumption of ethanol in adult rats and humans leads to reduced AVP-producing neurons, and prenatal ethanol (PE) exposure has been reported to cause changes in the morphology of AVP-producing cells in the suprachiasmatic nucleus of young rats. The present studies further characterize the effects of PE exposure on AVP in the young adult rat, its hypothalamic synthesis, pituitary storage, and osmotically stimulated release. Pregnant rats were fed a liquid diet with 35% of the calories from ethanol or a control liquid diet for days 7-22 of pregnancy. Water consumption and urine excretion rate were measured in the offspring at 60-68 days of age. Subsequently, the offspring were infused with 5% NaCl at 0.05 ml.kg(-1).min(-1) with plasma samples taken before and at three 40-min intervals during infusion for measurement of AVP and osmolality. Urine output and water intake were approximately 20% greater in PE-exposed rats than in rats with no PE exposure, and female rats had a greater water intake than males. The relationship between plasma osmolality and AVP in PE-exposed rats was parallel to, but shifted to the right of, the control rats, indicating an increase in osmotic threshold for AVP release. Pituitary AVP was reduced by 13% and hypothalamic AVP mRNA content was reduced by 35% in PE-exposed rats. Our data suggest that PE exposure can cause a permanent condition of a mild partial central diabetes insipidus.

Background: An increase in urinary albumin excretion (UAE) represents an early predictor of glomerular damage in diabetes mellitus (DM) and a risk factor for cardiovascular complications in hypertension. Vasopressin is elevated in DM and in some forms of hypertension. Previous studies in rats suggested that this hormone could play a role in the albuminuria observed in chronic renal failure or diabetic nephropathy, but no information is available concerning the mechanism of these effects and the possible influence of vasopressin on UAE in the healthy kidney. The present study was thus designed to evaluate whether vasopressin influences UAE in normal rats and humans, whether this effect is V(2)-receptor-dependent, and whether it is mediated by the renin-angiotensin system., Methods: UAE was measured in normal Wistar rats and healthy humans, or in subjects with various forms of diabetes insipidus (DI), before and after acute or chronic infusion of the vasopressin V(2) receptor agonist dDAVP. Chronic dDAVP administration was also performed in normal Wistar rats previously submitted to either chronic angiotensin-converting enzyme inhibition (ACEI) or chronic blockade of AT1 receptors (ARB)., Results: In rats, acute or chronic dDAVP infusion increased UAE significantly and reversibly (4-fold and 6-fold, respectively). In healthy subjects, acute infusion of dDAVP tripled UAE (P<0.01) but did not change creatinine and beta(2)-microglobulin excretion, thus suggesting that the rise in UAE was due to an increased glomerular leakage of albumin. dDAVP also increased UAE in patients with central DI and in patients with hereditary nephrogenic DI bearing AQP2 mutations. However, UAE was not increased in patients with hereditary nephrogenic DI bearing mutations of the V(2) receptor. In rats, ACEI and ARB blunted the dDAVP-induced rise in UAE by 70% (P<0.05) and 50% (NS), respectively., Conclusions: The present studies reveal for the first time that vasopressin induces a marked increase in UAE in healthy rats and humans. This albuminuric effect seems to result from increased glomerular leakage, requires functional vasopressin V(2) receptors, and is, at least in part, mediated by the renin-angiotensin system. These results bring additional support for an involvement of vasopressin in the albuminuria observed in pathological states such as diabetes mellitus or hypertension.

Adipsic diabetes insipidus (ADI) occurs in association with a heterogeneous group of conditions. We report vasopressin (AVP) responses to hypotension in nine patients with ADI and nine controls. Hypertonic saline infusion produced absent thirst (1.7 +/- 1.7 to 1.5 +/- 1.7 cm, P = 0.99) and AVP responses (0.3 +/- 0.1 to 0.4 +/- 0.1 pmol/liter, P = 0.99) in the ADI group, who also drank less than the control group (258 +/- 200 ml vs. 1544 +/- 306 ml, P < 0.001). Intravenous infusion of trimetaphan camsylate produced a fall in mean arterial pressure of 31.6% +/- 8.9% in patients and 29.4% +/- 6.1% in controls. Plasma AVP concentrations rose from 1.4 +/- 0.8 to 340.3 +/- 497.4 pmol/liter (P < 0.001) in the control group. In three patients with craniopharyngioma, there was no rise in plasma AVP concentrations (0.3 +/- 0.1 to 0.3 +/- 0.1 pmol/liter, P = 0.96), but plasma AVP rose significantly in response to hypotension in the other six patients (0.4 +/- 0.2 to 204.5 +/- 223.2 pmol/liter, P < 0.001). We concluded that the AVP responses to hypotension in ADI are heterogeneous and reflect the site of the lesion causing the diabetes insipidus.

Familial neurohypophysial diabetes insipidus (FNDI) is an autosomal dominant trait in which expression of a mutant vasopressin prohormone reduces vasopressin production. We investigated the NP85 Cys-->Gly mutant vasopressin prohormone in a large kindred in The Netherlands. We demonstrate that growth retardation is an important early sign in two children from this kindred, which recuperates by substitution therapy with 1-desamino-8-D-arginine vasopressin. To obtain clues about the basis for the dominant inheritance of FNDI, we analyzed the trafficking and processing of the mutant vasopressin prohormone in cell lines by metabolic labeling and immunoprecipitation. The mutant vasopressin prohormone was retained in the endoplasmic reticulum and thus was not processed to vasopressin. This defect was not caused by dimerization of the vasopressin prohormone via its unpaired cysteine residue. High level expression of the mutant vasopressin prohormone in cell lines resulted in strong accumulation in the endoplasmic reticulum and an altered morphology of this organelle. We hypothesize that disturbance of the endoplasmic reticulum results in dysfunction and ultimately cell death of the cells expressing the mutant prohormone. Our data support the hypothesis that FNDI is a progressive neurodegenerative disease with delayed onset of symptoms. Its treatment requires early detection of symptoms for which growth parameters are useful.

We analyzed the disorder of water metabolism in a 32 year-old female with chronic hypernatremia. She had meningitis at 4 years, and ventriculo-peritoneal shunt operation at 13 years because of normal pressure hydrocephalus. At 14 years hypernatremia of 166 mmol/l was initially found and thereafter hypernatremia ranging from 150 to 166 mmol/l has been persisted for the last 18 years. Physical and laboratory findings did not show dehydration. Urine volume was 750-1700 ml per day and urinary osmolality (Uosm) 446-984 mmol/kg, suggesting no urinary concentrating defect. Plasma arginine vasopressin (AVP) levels ranged from 0.4 to 1.2 pmol/l despite hyperosmolality of 298 through 343 mmol/kg under ad libitum water drinking. There was no correlation between plasma osmolality (Posm) and plasma AVP levels, but Uosm had a positive correlation with Posm (r=0.545, P < 0.05). Hypertonic saline (500 NaCl) infusion after a water load increased Uosm from 377 to 679 mmol/kg, and plasma AVP from 0.2 to 1.3 pmol/l. There was a positive correlation between Posm and plasma AVP levels in the hypertonic saline test (r=0.612, P<0.05). In contrast, an acute water load (20 ml/kg BW) verified the presence of impaired water excretion, as the percent excretion of the water load was only 8.5% and the minimal Uosm was as high as 710 mmol/kg. Urinary excretion of aquaporin-2 remained low in concert with plasma AVP levels. No abnormality in pituitary-adrenocortical function was found. These results indicate that marked hypernatremia is derived from partial central diabetes insipidus and elevated threshold of thirst, and that enhanced renal water handling may contribute to maintenance of body water in the present subject.

TGR(ASrAOGEN)680, a newly developed transgenic rat line with specific downregulation of astroglial synthesis of angiotensinogen, exhibits decreased brain angiotensinogen content associated with a mild diabetes insipidus and lower blood pressure. Autoradiographic experiments were performed on TGR(ASrAOGEN) (TG) and Sprague-Dawley (SD) control rats to quantify AT(1) and AT(2) receptor-binding sites in different brain nuclei and circumventricular organs. Dose-response curves for drinking response to intracerebroventricular injections of ANG II were compared between SD and TG rats. In most of the regions inside the blood-brain barrier [paraventricular nucleus (PVN), piriform cortex, lateral olfactory tract (LOT), and lateral preoptic area (LPO)], AT(1) receptor binding (sensitive to CV-11974) was significantly higher in TG compared with SD. In contrast, in the circumventricular organs investigated [subfornical organ (SFO) and area postrema], AT(1) receptor binding was significantly lower in TG. AT(2) receptors (binding sensitive to PD-123319) were detected at similar levels in the inferior olive (IO) of both strains. Angiotensin-binding sites sensitive to both CV-11974 and PD-123319 were detected in the LPO of SD rats and specifically upregulated in LOT, IO, and most notably PVN and SFO of TG. The dose-response curve for water intake after intracerebroventricular injections showed a higher sensitivity to ANG II of TG (EC(50) = 3.1 ng) compared with SD (EC(50) = 11.2 ng), strongly suggesting that the upregulation of AT(1) receptors inside the blood-brain barrier of TG rats is functional. Finally, we showed that downregulation of angiotensinogen synthesized by astroglial cells differentially regulates angiotensin receptor subtypes inside the brain and in circumventricular organs.

Background: Several mechanisms in the body regulate the water transport within the cells up and down during physiological and pathological conditions. The discovery of aquaporins, water channel proteins, has brought more insight into and understanding of how water crosses plasma membranes within cells in body tissue., Material and Methods: The functions of aquaporins are not fully understood; this paper summarise current knowledge of various aquaporins., Results: Known aquaporins are discussed in relation to some physiological, pathological and clinical conditions., Interpretation: In the future, measurements of aquaporin concentrations in urine and possibly in other samples will give us a broader picture of water exchange and a better understanding of the mechanisms underlying water production in clinical states like renal and heart failure and liver insufficiency. Moreover, by manipulating water channel proteins by compounds developed for this purpose, one may have a tool for treating some clinical disorders in which water depletion or water overload is an important factor.

Familial neurohypophyseal diabetes insipidus (FNDI) is an autosomal dominant disorder of renal water conservation due to deficiency of arginine vasopressin as the result of mutations in the arginine vasopressin-neurophysin II (AVP-NPII) gene that encodes the hormone or its carrier protein. Thirty-one different mutations have been reported. In this study, we evaluated the AVP-NPII gene in a family with FNDI and identified a new mutation (1911Gright curved arrow A) in the coding sequence for NPII in affected family members. This mutation substitutes Tyr for 74 Cys in the NPII moiety. NPII is an intracellular carrier protein for AVP during the axonal transport from the hypothalamus to the posterior pituitary and contains 14 conserved cysteine residues forming 7 disulfide bonds. Because the mutation cosegregates with the phenotype, it is possible that this mutation causes neurohypophyseal diabetes insipidus in this family.

Animal models of genetic hormone deficiency are useful as models for physiological studies of hormone deficiency and hormone action. Structure-function studies of the specific underlying gene defect may help in understanding mechanisms regulating gene expression and secretion of the peptide product. Spontaneous genetic models of vasopressin deficiency, such as the Brattleboro rat and human familial diabetes insipidus, have facilitated many studies of vasopressin. However, the Brattleboro rat may not be an ideal model of genetic vasopressin deficiency and therefore could be less useful for studies of the central nervous system or as a background strain for the introduction of new vasopressin gene constructs. The human model is appropriately limited by the constraints of human studies, so that engineered animal models of specific diseases, such as familial neurohypophysial diabetes insipidus, are required. The recent development of a vasopressin-null mouse may provide insights into the various roles of vasopressin in the stress response, cardiovascular regulation and behaviour. Additionally, animals with a complete genetic deficiency of vasopressin can serve as a background strain for introduction of novel vasopressin gene constructs to enable sophisticated studies of the regulation of vasopressin expression and the intracellular processes required for appropriate secretion of vasopressin peptide. As advanced techniques of genetic manipulation become more reliable, conditional expression of vasopressin, regulated by time or body site will permit even more detailed studies in this field.

Cytoplasmic autoantibodies to vasopressin-cells (AVPcAb) have been detected not only in patients with overt central diabetes insipidus (CDI), but also in patients with endocrine autoimmune diseases without CDI. This suggests that complete CDI can be preceded by a preclinical stage. Among 878 patients with endocrine autoimmune diseases without CDI, 9 patients found to be AVPcAb positive and 139 AVPcAb-negative controls were enrolled in this open prospective study. They were evaluated for AVPcAb and posterior pituitary function at least yearly for about 4 yr (range, 37-48 months); during this span, magnetic resonance imaging (MRI) of posterior pituitary and stalk was performed only in the AVPcAb-positive patients. Five of the 9 AVPcAb-positive patients had normal posterior pituitary function at study entry. They were AVPcAb positive throughout the follow-up period. At later stages of the study, 3 of them developed partial CDI, and 1 developed complete CDI. The remaining 4 patients showed impaired response to the water deprivation test at study entry and were diagnosed as having partial CDI. Two of them agreed to receive desmopressin replacement for 1 yr. After this treatment, the patients became negative for AVPcAb and displayed normal posterior pituitary function until the end of the follow-up. Conversely, the 2 untreated patients with partial CDI remained AVPcAb positive. One of them developed overt CDI. None of the controls became AVPcAb positive or developed CDI. The normal hyperintense MRI signal of the posterior pituitary, present at study entry, persisted subsequently in all 9 AVPcAb-positive patients, including those developing overt CDI, only disappearing in the late phase of complete CDI. In asymptomatic subjects, the monitoring of AVPcAb, but not MRI, seems to be useful to predict a progression toward partial/overt CDI. Early desmopressin therapy in patients with partial CDI could interrupt or delay the autoimmune damage and the progression toward clinically overt CDI.

Diabetic nephropathy represents a major complication of diabetes mellitus (DM), and the origin of this complication is poorly understood. Vasopressin (VP), which is elevated in type I and type II DM, has been shown to increase glomerular filtration rate in normal rats and to contribute to progression of chronic renal failure in 5/6 nephrectomized rats. The present study was thus designed to evaluate whether VP contributes to the renal disorders of DM. Renal function was compared in Brattleboro rats with diabetes insipidus (DI) lacking VP and in normal Long-Evans (LE) rats, with or without streptozotocin-induced DM. Blood and urine were collected after 2 and 4 weeks of DM, and creatinine clearance, urinary glucose and albumin excretion, and kidney weight were measured. Plasma glucose increased 3-fold in DM rats of both strains, but glucose excretion was approximately 40% lower in DI-DM than in LE-DM, suggesting less intense metabolic disorders. Creatinine clearance increased significantly in LE-DM (P < 0.01) but failed to increase in DI-DM. Urinary albumin excretion more than doubled in LE-DM but rose by only 34% in DI-DM rats (P < 0.05). Kidney hypertrophy was also less intense in DI-DM than in LE-DM (P < 0.001). These results suggest that VP plays a critical role in diabetic hyperfiltration and albuminuria induced by DM. This hormone thus seems to be an additional risk factor for diabetic nephropathy and, thus, a potential target for prevention and/or therapeutic intervention.

The aim of this open prospective randomized study was to evaluate the effect of a 6-month treatment with alendronate on the bone mineral density (BMD) at lumbar spine in patients with central diabetes insipidus. Eighteen patients with central diabetes insipidus and 18 sex- and age-matched healthy subjects entered this study. At study entry, all subjects underwent BMD assessment at the lumbar spine and measurement of serum osteocalcin (OC) and cross-linked N-telopeptides of type I collagen (Ntx). Thereafter, 9 of the 18 patients were randomized to receive treatment with alendronate at a dose of 10 mg, orally, once daily for 6 months (group 1), whereas the remaining 9 patients did not receive any treatment affecting bone status during this period (group 2). After 6 months, bone metabolism and bone density study were repeated in all patients. At baseline, lumbar BMD values (0.86+/-0.03 vs. 1.01+/-0.02 g/cm2; P<0.001) and serum OC levels (4.7+/-0.3 vs. 7.9+/-0.2 microg/L; P<0.001) were significantly lower, whereas urinary Ntx levels were significantly higher [72.0+/-1.9 vs. 64.6+/-1.7 nmol bone collagen equivalents (BCE)/nmol creatinine (Cr); P<0.01] in patients than in controls. After randomization, no difference in lumbar BMD, serum OC, or urinary Ntx was found between patients of group 1 and group 2. At the 6 month follow-up, no difference in serum OC levels was found compared to baseline evaluation in patients of both group 1 and group 2. By contrast, a significant decrease in urinary Ntx levels was found in patients of group 1 (70.3+/-3.0 vs. 75.4+/-2.1 nmol BCE/nmol Cr; P<0.05), but not in patients of group 2 (68.8+/-3.3 vs. 68.5+/-3.0 nmol BCE/nmol Cr; P = NS). A significant increase in lumbar BMD values was found in patients of group 1 (0.88+/-0.04 vs. 0.83+/-0.04 g/cm2; P<0.05), whereas a significant decrease in lumbar BMD values was found in patients of group 2 (0.86+/-0.05 vs. 0.89+/-0.05 g/cm2; P<0.05). Lumbar BMD increased 7.0+/-1.5% in patients of group 1 and decreased 4.2+/-1.8% in patients of group 2 (P<0.001). In conclusion, this study demonstrated that a 6-month treatment with alendronate in patients with central diabetes insipidus was effective in significantly improving BMD at the lumbar spine, which was significantly worsened in untreated patients. Therefore, alendronate treatment could be used in patients with central diabetes insipidus with documented osteopenia or osteoporosis.

Angiotensin produced systemically or locally in tissues such as the brain plays an important role in the regulation of blood pressure and in the development of hypertension. We have established transgenic rats [TGR(ASrAOGEN)] expressing an antisense RNA against angiotensinogen mRNA specifically in the brain. In these animals, the brain angiotensinogen level is reduced by more than 90% and the drinking response to intracerebroventricular renin infusions is decreased markedly compared with control rats. Blood pressure of transgenic rats is lowered by 8 mmHg (1 mmHg = 133 Pa) compared with control rats. Crossbreeding of TGR(ASrAOGEN) with a hypertensive transgenic rat strain exhibiting elevated angiotensin II levels in tissues results in a marked attenuation of the hypertensive phenotype. Moreover, TGR(ASrAOGEN) exhibit a diabetes insipidus-like syndrome producing an increased amount of urine with decreased osmolarity. The observed reduction in plasma vasopressin by 35% may mediate these phenotypes of TGR(ASrAOGEN). This new animal model presenting long-term and tissue-specific down-regulation of angiotensinogen corroborates the functional significance of local angiotensin production in the brain for the central regulation of blood pressure and for the pathogenesis of hypertension.

The aim of the current study was to evaluate the biochemical parameters of bone metabolism and the bone mineral density (BMD) in patients with central diabetes insipidus, either treated or not treated with endonasal desmopressin. Eighteen patients with central diabetes insipidus and 18 sex- and age-matched healthy subjects entered the study. The patients were divided into 2 groups: patients who did not receive treatment with desmopressin for at least 1 yr (group 1), and patients chronically treated with desmopressin since the diagnosis of diabetes insipidus (group 2). Serum osteocalcin and urinary cross-linked N-telopeptide of type I collagen levels were measured in all patients and controls using RIA and enzyme-linked immunosorbent assay kits, respectively. BMD was measured at the lumbar spine (L1-L4) and at the femoral neck in all subjects, using a Hologic QDR 1000 analyzer (Hologic Inc., Waltham, MA). Serum osteocalcin concentrations were significantly lower, both in patients of group 1 and group 2, compared with healthy subjects (5.1 +/- 0.6 and 4.5 +/- 0.3 vs. 7.9 +/- 0.2 micrograms/L, P < 0.05), whereas urinary cross-linked N-telopeptide of type I collagen concentrations were similar in the three groups of subjects (72.8 +/- 2.2, 71.6 +/- 2.7, and 64.6 +/- 1.7 nmol bone collagen equivalent/mmol creatinine). BMD was significantly decreased in patients of groups 1 and 2, compared with controls, both at lumbar spine (0.84 +/- 0.06 and 0.87 +/- 0.04 vs. 1.01 +/- 0.02 g/cm2, P < 0.05) and femoral neck (0.78 +/- 0.06 and 0.80 +/- 0.04 vs. 0.93 +/- 0.02 g/cm2, P < 0.05). A significant inverse correlation was found between disease duration and BMD values, evaluated as T scores, both at lumbar spine (group 1: r = -0.952, P < 0.005; group 2: r = -0.921, P < 0.001) and at femoral neck (group 1: r = -0.914, P < 0.05; group 2: r = -0.683, P < 0.05). In conclusion, patients with central diabetes insipidus had a significant bone impairment, compared with healthy subjects. Replacement with endonasal desmopressin at standard doses was not able to prevent or reverse the bone impairment. These findings suggest that, in patients with central diabetes insipidus, bone status analysis is mandatory; and a bone-loss preventing treatment might be beneficial.

1. The mechanism underlying the antidiuretic effect of thiazide diuretics in diabetes insipidus (DI) is unknown. This study addressed two specific questions: is the reduction in urine flow rate (V) related to a decrease in the delivery of fluid from the pars recta of the proximal tubules ('distal delivery'), and are there any changes in the expression and/or intracellular distribution of vasopressin stimulated water channels (AQP2) in the collecting ducts, during chronic thiazide-induced antidiuresis? 2. Nine Brattleboro rats with vasopressin-deficient DI were treated for 5 days with bendroflumethiazide (BFTZ), 9 mg kg(-1) day(-1) orally, and 9 Brattleboro rats were left untreated. BFTZ-treated DI rats showed a fall in V from approximately 200 to approximately 75 ml day(-1) and an increase in urine osmolality from approximately 130 to approximately 400 mosmol kg(-1). 3. BFTZ-induced antidiuresis was associated with a persistent loss of sodium, but not of potassium. After 5 days of treatment, clearance studies in conscious rats showed a tendency towards decreases in effective renal plasma flow (-7%), GFR (-12%) and lithium clearance (C(Li); used as marker for distal delivery) (-25%), compared with untreated controls, but none of these changes were statistically significant. There was no apparent relationship between C(Li) and V in BFTZ-treated or untreated DI rats. 4. BFTZ treatment did not change the expression of AQP2 in homogenates of cortex, outer or inner medulla from DI rats, or from normal Long Evans rats. Light and electron microscopic immunocytochemistry revealed no changes in intracellular distribution of AQP2 in principal cells from inner medullary collecting ducts of BFTZ-treated DI rats. 5. We concluded, (i) that although the antidiuretic effect of BFTZ in rats with DI is associated with a net loss of Na, the decrease in V shows no association with changes in distal delivery, as estimated by C(Li). (ii) Antidiuretic treatment with BFTZ does not alter the expression of subcellular distribution of AQP2 water channels in the collecting ducts. The mechanism underlying the chronic antidiuresis caused by thiazide diuretics in DI remains elusive.

Autosomal dominant neurohypophyseal diabetes insipidus (ADNDI) is an inherited disease caused by progressive degeneration of the magnocellular neurons of the hypothalamus leading to decreased ability to produce the hormone arginine vasopressin (AVP). Affected individuals are not symptomatic at birth, but usually develop diabetes insipidus at 1-6 yr of age. The genetic locus of the disease is the AVP-neurophysin II (NPII) gene, and mutations that cause ADNDI have been found in both the signal peptide of the prepro-AVP-NPII precursor and within NPII itself. An affected girl who presented at 9 months of age and her similarly affected younger brother and father were all found to have a novel missense mutation (G1758-->T) encoding the amino acid substitution Gly23-->Val within NPII. The mutation was confirmed by restriction endonuclease analysis. A T1-weighted magnetic resonance imaging of the father's pituitary gland demonstrates an attenuated posterior pituitary bright spot. This mutation may be valuable for developing models of dominantly inherited neurodegeneration, as the early age of onset of symptoms suggests that this mutation may be particularly deleterious to the magnocellular neuron.

We present six cases of diabetes insipidus (DI) complicating pregnancy. In three cases, DI was manifested during pregnancy and required the administration of desmopressin acetate (1-desamino-8-D-arginine vasopressin, DDAVP). All these cases exhibited abnormal laboratory data such as an elevation of liver enzymes or a decrease in serum antithrombin III. The remaining three cases had suffered from DI before pregnancy which was well controlled on DDAVP. The clinical courses of these pregnancies were all uneventful subsequent to therapy. If DI is first recognized during pregnancy, attention should be paid to the possibility of abnormal liver function and eclampsia.

The objective of the present study was to examine the effect of changes in plasma osmolality (pOsm) on the responses of the pituitary-adrenal axis to CRH and atrial natriuretic peptide (ANP) release in patients with central diabetes insipidus (DI). Eight normal subjects and six DI patients were subjected to human CRH (hCRH) (1 microgram/kg) stimulation alone or associated with isotonic volume loading (0.9% NaCl, 12 mL.kg.60 min) or an osmotic stimulus (5% NaCl, 0.06 mL.kg/min.120 min). The DI group showed significantly increased pOsm and undetectable or low plasma arginine vasopressin (AVP) during all tests. In the control group, pOsm and plasma AVP increased only during the osmotic stimulus. The DI group presented lower plasma ANP levels than controls during osmotic stimulus and isotonic volume loading. The lower ANP secretion in DI patients corroborates the importance of neurohypophyseal hormones in ANP regulation. Basal plasma ACTH and cortisol levels did not differ between controls and DI. The latter group presented a higher ACTH response than controls during stimulation with hCRH alone [area under the curve (AUC) 1138 +/- 99 vs. 709 +/- 62 pmol.L/min] and hCRH/5% NaCl (AUC 1602 +/- 209 vs. 1158 +/- 187 pmol.L.min). The DI cortisol AUC were higher than controls during stimulation with hCRH alone (65,471 +/- 6,070 vs. 48,062 +/- 3,476 nmol.L.min) and hCRH/5% NaCl (89,005 +/- 10,043 vs. 62,105 +/- 5,600 nmol.L.min). The highest ACTH and cortisol responses to hCRH in both groups were obtained with hCRH/5% NaCl. There was a significant correlation between mean pOsm and ACTH response to hCRH (r = 0.62). The increased responses to hCRH with increasing pOsm were present in control subjects and in patients with DI. However, at any given level of pOsm, there was no difference in ACTH response between controls and DI. These data indicate that the acute increases in pOsm augmented the ACTH and cortisol responses to hCRH that involve other factors besides magnocellular AVP.

Autosomal dominant neurohypophyseal diabetes insipidus (ADNDI) is a familial form of diabetes insipidus due to progressive vasopressin deficiency with onset typically at 1-6 yr of age. Affected individuals demonstrate specific degeneration of the vasopressinergic magnocellular neurons in the hypothalamic supraoptic and paraventricular nuclei and loss of the posterior pituitary bright spot on magnetic resonance imaging. The genetic locus of ADNDI is the arginine vasopressin-neurophysin II (AVP-NPII) gene. Mutations that cause ADNDI have been found to occur both within the signal peptide of the prepro-AVP-NPII precursor and within the coding sequence for neurophysin II, but not within the coding sequence for AVP itself. We evaluated the AVP-NPII genes in two independent families with ADNDI and identified a mutation (C280-->T) in the coding sequence for the signal peptide of the prepro-AVP-NPII precursor in both families. This mutation encodes an Ala-->Val substitution at the C-terminus of the signal peptide (-1 amino acid). This mutation predicts the complete inability of signal peptidase to cleave the signal peptide from the preproprecursor and supports the hypothesis that the progressive neural degeneration that underlies ADNDI is caused by accumulation of malprocessed precursor. However, considerable heterogeneity in the age of onset (1-28 yr of age) and the severity of diabetes insipidus among affected members of these two families suggests that additional factors modulate the rate and extent of progression of the neurodegeneration that results from this one specific ADNDI mutation.