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Background: Congenital isolated growth hormone deficiency (IGHD) is a rare endocrine disorder that presents with severe proportionate growth failure. Dominant (type II) IGHD is usually caused by heterozygous mutations of GH1. The presentation of newly affected family members in 3 families with dominant IGHD in whom previous genetic testing had not demonstrated a GH1 mutation or had not been performed, prompted us to identify the underlying genetic cause. Methods:GH1 was sequenced in 3 Caucasian families with a clinical autosomal dominant IGHD. Results: All affected family members had severe growth hormone (GH) deficiency that became apparent in the first 2 years of life. GH treatment led to a marked increase in height SDS. So far, no other pituitary dysfunctions have become apparent. In the first family a novel splice site mutation in GH1 was identified (c.172-1G>C, IVS2-1G>C). In two other families a previously reported splice site mutation (c.291+1G>A, IVS3+1G>A) was found. Conclusion: These data show that several years after negative genetic testing it was now possible to make a genetic diagnosis in these families with a well-defined, clearly heritable, autosomal dominant IGHD. This underscores the importance of clinical and genetic follow-up in a multidisciplinary setting. It also shows that even without a positive family history, genetic testing should be considered if the phenotype is strongly suggestive for a genetic syndrome. Identification of pathogenic mutations, like these GH1 mutations, has important clinical implications for the surveillance and genetic counseling of patients and expands our knowledge on the genotype-phenotype correlation. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

A 13-year-old phenotypically female patient presented with short stature (height SDS -2.6), but without any Turner stigmata or other dysmorphic features. Chromosome analysis showed mosaicism for an isodicentric (idic) (Y)(q11.23) containing cell line and a 45,X cell line. Subsequent gonadectomy revealed a left streak ovary and a right ovary of abnormal appearance, which on histological examination appeared to contain a gonadoblastoma. DNA analysis showed that the proposed critical region of the gonadoblastoma locus on the Y chromosome was contained within the patient's idic (Y). Conclusion. The case described here shows that patients with 45,X/46,X, isodicentric (Yp) mosaicism and a female phenotype (1) can lack external virilisation but still have a gonadoblastoma and (2) do not necessarily have Turner stigmata but can present with only short stature. This case also underlines the importance of karyotyping patients with unexplained short stature to enable gonadectomy if Y-derived material is detected. [ABSTRACT FROM AUTHOR]

Unlabelled: The persistent müllerian duct syndrome, characterized by the presence of uterus and tubes in males, is a familial disorder due to defects of synthesis or action of anti-müllerian hormone, a Sertoli cell glycoprotein responsible for the regression of müllerian derivatives in normal male fetuses. Patients are normally virilized and testicular production of testosterone is normal. Both testes may be cryptorchid; alternatively, one may be descended into the inguinal canal or scrotum, together with the müllerian derivatives, a condition known as "hernia uteri inguinalis". We have recently observed three patients affected by the persistent müllerian duct syndrome who experienced progressive degeneration of testicular tissue. In two, functional testicular tissue was still present some months after birth, but deteriorated progressively later. In one patient, testicular tissue was already absent at birth, but the normal virilization of external genitalia indicated that testicular degeneration must have occurred late during fetal life, after the expected time of regression of male müllerian ducts.Conclusion: The high incidence of degeneration of testicular tissue in the persistent müllerian duct syndrome could be indirectly linked to anatomical abnormalities which could favour testicular torsion, known to induce testicular regression. [ABSTRACT FROM AUTHOR]

Examines the Tpit gene coding sequence in patients with neonatal onset form of congenital isolated ACTH deficiency. Mutation of Tpit in several patients; Identification of several compound heterozygotes involving different mutations; Total number of families that suffered a neonatal death.

Persistent hyperinsulinemic hypoglycemia of infancy or congenital hyperinsulinism of the neonate is a rare condition that may cause severe neurologic damage if the disease is unrecognized or inadequately treated. Current treatment aims to restore normal blood glucose levels by providing a carbohydrate-enriched diet and drugs that inhibit insulin secretion. If medical treatment fails, then surgery is required. Because congenital hyperinsulinism may be caused either by diffuse involvement of pancreatic beta-cells or by a focal cluster of abnormal beta-cells, the extent of pancreatectomy varies. We report on 2 patients with a focal form of the disease for whom diagnosis was made with laparoscopy. Laparoscopic enucleation of the lesion was curative. [ABSTRACT FROM AUTHOR]

Background: Congenital isolated growth hormone deficiency (IGHD) is a rare endocrine disorder that presents with severe proportionate growth failure. Dominant (type II) IGHD is usually caused by heterozygous mutations of GH1. The presentation of newly affected family members in 3 families with dominant IGHD in whom previous genetic testing had not demonstrated a GH1 mutation or had not been performed, prompted us to identify the underlying genetic cause., Methods: GH1 was sequenced in 3 Caucasian families with a clinical autosomal dominant IGHD., Results: All affected family members had severe growth hormone (GH) deficiency that became apparent in the first 2 years of life. GH treatment led to a marked increase in height SDS. So far, no other pituitary dysfunctions have become apparent. In the first family a novel splice site mutation in GH1 was identified (c.172-1G>C, IVS2-1G>C). In two other families a previously reported splice site mutation (c.291+1G>A, IVS3+1G>A) was found., Conclusion: These data show that several years after negative genetic testing it was now possible to make a genetic diagnosis in these families with a well-defined, clearly heritable, autosomal dominant IGHD. This underscores the importance of clinical and genetic follow-up in a multidisciplinary setting. It also shows that even without a positive family history, genetic testing should be considered if the phenotype is strongly suggestive for a genetic syndrome. Identification of pathogenic mutations, like these GH1 mutations, has important clinical implications for the surveillance and genetic counseling of patients and expands our knowledge on the genotype-phenotype correlation., (© 2013 S. Karger AG, Basel.)

Background: Treatment with a specific HSP60 epitope in new onset of type 1 diabetes (T1D) patients has been shown to preserve endogenous insulin production. Previously, recognition of pan HLA-DR-binding HSP60 epitopes in various autoimmune diseases was found; this study investigated recognition of these epitopes in newly diagnosed T1D patients and correlated findings to the occurrence of a partial remission., Methods: Peripheral blood mononuclear cells of 18 children with T1D were prospectively collected at disease onset and a few months after diagnosis. Epitope-specific T-cell proliferation and cytokine production (intracellular and in culture supernatants) were measured. Results were compared with 31 longstanding T1D patients and ten healthy controls., Results: Although HSP60 epitope-specific T-cell proliferative responses were detected, overall proliferative responses were low. At onset, epitope-specific intracellular IFN-γ production was higher in T1D patients compared with healthy controls (p < 0.05). At follow-up, both IL-10 and IFN-γ production were higher in those without a partial remission than in those with a partial remission (both p < 0.05). Also, IL-10 and IFN-γ production were higher compared with onset for patients without a PR (both p < 0.01). In supernatants of HSP60 epitope-specific T-cell cultures, no substantial differences in cytokine production were found between T1D patients with and without a partial remission, either at onset or a few months after onset. As patient numbers were small, results should be interpreted with caution., Conclusions: Pan-DR-binding HSP60 peptides induced low peptide-specific proliferative responses and peptide-specific production of some, mainly intracellular, cytokines in T1D patients. Recognition did not differ significantly between patient groups and various time points., (Copyright © 2012 John Wiley & Sons, Ltd.)

Background: Congenital generalized lipodystrophy (CGL) results from mutations in AGPAT2, encoding 1-acyl-glycerol-3-phosphate-acyltransferase 2 (CGL1; MIM 608594), BSCL2, encoding seipin (CGL2; MIM 269700), CAV1, encoding caveolin1 (CGL3; MIM 612526) or PTRF, encoding polymerase I and transcript release factor (CGL4; MIM 613327). This study aims to investigate the genotype/phenotype relationship and search for a possible pathogenic mechanism in a patient with CGL., Design: Case report., Patients and Setting: A 7-day-old child of consanguineous Turkish parents presented with a generalized loss of subcutaneous fat. He had a strikingly enlarged liver, high serum triglycerides, and hyperglycaemia, suggestive for CGL., Results: A novel homozygous mutation in the acceptor splice site of exon 5 of the BSCL2 gene was found in the genome of the proband. This mutation causes a complex RNA splicing defect and results in two different aberrant seipin proteins, which were normally expressed and localized to the endoplasmic reticulum like wild type protein. Analysis of the patient's urine showed intermittent elevations of citric acid intermediates and persistently high concentrations of ethylmalonic acid, suggestive of a disturbance of the mitochondrial respiratory chain., Conclusion: Here we report abnormal urinary organic acid levels, indicative of mitochondrial dysfunction, in a patient with CGL resulting from a novel mutation in BSCL2. Our findings suggest for the first time an association between CGL and secondary mitochondrial dysfunction.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare autosomal recessive organ-specific autoimmune disorder that is characterized by a variable combination of (i) chronic mucocutaneous candidiasis, (ii) polyendocrinopathy and/or hepatitis and (iii) dystrophy of the dental enamel and nails. We analyzed the AIRE (autoimmune regulator) gene in subjects who presented any symptom that has been associated with APECED, including candidiasis and autoimmune endocrinopathy. We observed that 83.3% of patients presented at least two of the three typical manifestations of APECED, while the remaining 16.7% of patients showed other signs of the disease. Analysis of the genetic diagnosis of these subjects revealed that a considerable delay occurs in the majority of patients between the appearance of symptoms and the diagnosis. Overall, the mean diagnostic delay in our patients was 10.2 years. These results suggest that molecular analysis of AIRE should be performed in patients with relapsing mucocutaneous candidiasis for early identification of APECED., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Context: Mutations in DAX1 (dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome gene 1; NR0B1) cause X-linked adrenal hypoplasia congenita, a disease characterized by primary adrenal failure, testicular dysgenesis, and gonadotropin deficiency. Most DAX1 mutations are deletions, nonsense, or frameshift mutations that markedly impair its transcriptional activity. Missense mutations have been restricted to the carboxy-terminal domain and are associated with more variable clinical phenotypes., Objective: The objective was to identify novel clinical phenotypes associated with DAX1 missense mutations., Patients and Design: We investigated the genetic basis of isolated mineralocorticoid deficiency in a patient who carries a unique missense mutation (W105C) in the amino-terminal region of DAX1., Results: The W105C DAX1 mutation in the proband was present in three asymptomatic hemizygous males, but it was not detected in the general population. Using in vitro studies of DAX1 expression and function in transfected cells, we demonstrate that the mutant DAX1 protein exhibits mild loss of function, whether studied for genes it represses or for genes it activates. Structure-function studies suggest that the W105C and other mutations in the aminoterminus are compensated by the presence of repeated LXXLL motifs that mediate DAX1 interactions with other proteins., Conclusions: We describe the first missense mutation in the aminoterminus of DAX1 and conclude that mutations in this region may be partially compensated by redundant functional domains. Mild DAX1 mutations may be a cause of isolated mineralocorticoid deficiency.

Tpit is a T box transcription factor important for terminal differentiation of pituitary proopiomelanocortin-expressing cells. We demonstrated that human and mouse mutations of the TPIT gene cause a neonatal-onset form of congenital isolated ACTH deficiency (IAD). In the absence of glucocorticoid replacement, IAD can lead to neonatal death by acute adrenal insufficiency. This clinical entity was not previously well characterized because of the small number of published cases. Since identification of the first TPIT mutations, we have enlarged our series of neonatal IAD patients to 27 patients from 21 unrelated families. We found TPIT mutations in 17 of 27 patients. We identified 10 different TPIT mutations, with one mutation found in five unrelated families. All patients appeared to be homozygous or compound heterozygous for TPIT mutations, and their unaffected parents are heterozygous carriers, confirming a recessive mode of transmission. We compared the clinical and biological phenotype of the 17 IAD patients carrying a TPIT mutation with the 10 IAD patients with normal TPIT-coding sequences. This series of neonatal IAD patients revealed a highly homogeneous clinical presentation, suggesting that this disease may be an underestimated cause of neonatal death. Identification of TPIT gene mutations as the principal molecular cause of neonatal IAD permits prenatal diagnosis for families at risk for the purpose of early glucocorticoid replacement therapy.

Tpit is a highly cell-restricted transcription factor that is required for expression of the pro-opiomelanocortin (POMC) gene and for terminal differentiation of the pituitary corticotroph lineage. Its exclusive expression in pituitary POMC-expressing cells has suggested that its mutation may cause isolated deficiency of pituitary adrenocorticotropin (ACTH). We now show that Tpit-deficient mice constitute a model of isolated ACTH deficiency (IAD) that is very similar to human IAD patients carrying TPIT gene mutations. Through genetic analysis of a panel of IAD patients, we show that TPIT gene mutations are associated at high frequency with early onset IAD, but not with juvenile forms of this deficiency. We identified seven different TPIT mutations, including nonsense, missense, point deletion, and a genomic deletion. This work defines congenital early onset IAD as a relatively homogeneous clinical entity caused by recessive transmission of loss-of-function mutations in the TPIT gene.

Androgen insensitivity syndrome encompasses a wide range of phenotypes, which are caused by numerous different mutations in the AR gene. Detailed information on the genotype/phenotype relationship in androgen insensitivity syndrome is important for sex assignment, treatment of androgen insensitivity syndrome patients, genetic counseling of their families, and insight into the functional domains of the AR. The commonly accepted concept of dependence on fetal androgens of the development of Wolffian ducts was studied in complete androgen insensitivity syndrome (CAIS) patients. In a nationwide survey in The Netherlands, all cases (n = 49) with the presumptive diagnosis androgen insensitivity syndrome known to pediatric endocrinologists and clinical geneticists were studied. After studying the clinical phenotype, mutation analysis and functional analysis of mutant receptors were performed using genital skin fibroblasts and in vitro expression studies. Here we report the findings in families with multiple affected cases. Fifty-nine percent of androgen insensitivity syndrome patients had other affected relatives. A total of 17 families were studied, seven families with CAIS (18 patients), nine families with partial androgen insensitivity (24 patients), and one family with female prepubertal phenotypes (two patients). No phenotypic variation was observed in families with CAIS. However, phenotypic variation was observed in one-third of families with partial androgen insensitivity resulting in different sex of rearing and differences in requirement of reconstructive surgery. Intrafamilial phenotypic variation was observed for mutations R846H, M771I, and deletion of amino acid N682. Four newly identified mutations were found. Follow-up in families with different AR gene mutations provided information on residual androgen action in vivo and the development of the prepubertal and adult phenotype. Patients with a functional complete defective AR had some pubic hair, Tanner stage P2, and vestigial Wolffian duct derivatives despite absence of AR expression. Vaginal length was functional in most but not all CAIS patients. The minimal incidence of androgen insensitivity syndrome in The Netherlands, based on patients with molecular proof of the diagnosis is 1:99,000. Phenotypic variation was absent in families with CAIS, but distinct phenotypic variation was observed relatively frequent in families with partial androgen insensitivity. Molecular observations suggest that phenotypic variation had different etiologies among these families. Sex assignment of patients with partial androgen insensitivity cannot be based on a specific identified AR gene mutation because distinct phenotypic variation in partial androgen insensitivity families is relatively frequent. In genetic counseling of partial androgen insensitivity families, this frequent occurrence of variable expression resulting in differences in sex of rearing and/or requirement of reconstructive surgery is important information. During puberty or normal dose androgen therapy, no or only minimal virilization may occur even in patients with significant (but still deficient) prenatal virilization. Wolffian duct remnants remain detectable but differentiation does not occur in the absence of a functional AR. In many CAIS patients, surgical elongation of the vagina is not indicated.

17Beta-hydroxysteroid dehydrogenase-3 (17betaHSD3) deficiency is an autosomal recessive form of male pseudohermaphroditism caused by mutations in the HSD17B3 gene. In a nationwide study on male pseudohermaphroditism among all pediatric endocrinologists and clinical geneticists in The Netherlands, 18 17betaHSD3-deficient index cases were identified, 12 of whom initially had received the tentative diagnosis androgen insensitivity syndrome (AIS). The phenotypes and genotypes of these patients were studied. Endocrine diagnostic methods were evaluated in comparison to mutation analysis of the HSD17B3 gene. RT-PCR studies were performed on testicular ribonucleic acid of patients homozygous for two different splice site mutations. The minimal incidence of 17betaHSD3 deficiency in The Netherlands and the corresponding carrier frequency were calculated. Haplotype analysis of the chromosomal region of the HSD17B3 gene in Europeans, North Americans, Latin Americans, Australians, and Arabs was used to establish whether recurrent identical mutations were ancient or had repeatedly occurred de novo. In genotypically identical cases, phenotypic variation for external sexual development was observed. Gonadotropin-stimulated serum testosterone/androstenedione ratios in 17betaHSD3-deficient patients were discriminative in all cases and did not overlap with ratios in normal controls or with ratios in AIS patients. In all investigated patients both HSD17B3 alleles were mutated. The intronic mutations 325 + 4;A-->T and 655-1;G-->A disrupted normal splicing, but a small amount of wild-type messenger ribonucleic acid was still made in patients homozygous for 655-1;G-->A. The minimal incidence of 17betaHSD3 deficiency in The Netherlands was shown to be 1: 147,000, with a heterozygote frequency of 1:135. At least 4 mutations, 325 + 4;A-->T, N74T, 655-1;G-->A, and R80Q, found worldwide, appeared to be ancient and originating from genetic founders. Their dispersion could be reconstructed through historical analysis. The HSD17B3 gene mutations 326-1;G-->C and P282L were de novo mutations. 17betaHSD3 deficiency can be reliably diagnosed by endocrine evaluation and mutation analysis. Phenotypic variation can occur between families with the same homozygous mutations. The incidence of 17betaHSD3 deficiency is 0.65 times the incidence of AIS, which is thought to be the most frequent known cause of male pseudohermaphroditism without dysgenic gonads. A global inventory of affected cases demonstrated the ancient origin of at least four mutations. The mutational history of this genetic locus offers views into human diversity and disease, provided by national and international collaboration.

The islet amyloid polypeptide (IAPP) immunoreactivity of the adult rat pancreas is located in insulin-containing B cells as well as in somatostatin-containing D cells. In both cell types, the IAPP immunoreactivity is identical to rat synthetic IAPP in terms of its elution position after reversed phase HPLC and its binding to IAPP antibodies. The IAPP content per 10(6) B-cells is more than 100 fold lower than the corresponding insulin content, but comparable to the IAPP content of D cells. After induction of diabetes by streptozotocin, pancreatic IAPP seems predominantly located in somatostatin-containing cells. In normal rats, pancreatic insulin and IAPP content increase 20 fold from birth to 12 weeks of age; beyond week 12, the further rise in pancreatic insulin was not paralleled by an increase in IAPP content.

Previous studies in rodent islets have suggested the existence of a small number of proliferating islet cells. Since islet tissue is composed of endocrine as well as nonendocrine cells, we examined whether the DNA synthesis that is detectable in intact islets in vitro corresponds to an activity of islet B cells, islet endocrine non-B cells and/or nonendocrine islet cells. DNA synthesis was quantified by [3H]thymidine incorporation in trichloracetic acid precipitable material, by nuclear thymidine labeling in autoradiographs, and by nuclear bromodeoxyuridine fluorescence. Adult islet endocrine purified B cells, as well as other endocrine islet cells, incorporated 1 to 2 fmol thymidine/1000 cells, which is 3 times lower than intact islet tissue and 30 times lower than nonendocrine islet cells. Addition of 10% fetal calf serum did not increase DNA synthesis in purified endocrine islet cells but doubled it in intact islets and enhanced it 8-fold in nonendocrine islet cells. The higher thymidine incorporation in intact islets was due to the presence of nonendocrine cells. An increase in medium glucose concentration from 100 to 200 mg/100 ml doubled the thymidine incorporation in purified islet B cells, but not in other endocrine islet cells; no concomitant increase in the number of thymidine or bromodeoxyuridine-labeled nuclei was observed. A phenomenon of glucose-stimulated DNA repair was not excluded. Using three different methods, we have found no evidence for a proliferating activity of adult rat islet B cells under the selected in vitro conditions of this study.

Insulin and the insulin-like growth factors (IGFs) are chemically related polypeptides that interact with distinct receptors and elicit the same biological responses. We have sought a readily propagated cell line from a potential target tissue in which to probe the multiple and complex interrelationships among receptor and effector pathways for these polypeptides. We now report that the mouse muscle cell line BC3H-1 represents such a model system. BC3H-1 cells differentiate spontaneously at high density to form cells with muscle-specific properties, but do not fuse. Standaert et al. reported that differentiated BC3H-1 myocytes possess insulin receptors that mediate glucose and amino acid uptake and are down-regulated by prolonged incubation with insulin. The present report demonstrates that BC3H-1 myocytes also possess functional and regulated IGF receptors. Two subtypes of IGF receptors, types I and II, differing in structure and peptide specificity, were demonstrated by competitive binding and affinity cross-linking experiments. Low concentrations of IGFs stimulated glucose incorporation and alpha-aminoisobutyric acid uptake by BC3H-1 myocytes, suggesting that these effects were mediated primarily by IGF receptors rather than insulin receptors. Preincubation with IGFs (or high concentrations of insulin) selectively down-regulated type I IGF receptors without affecting type II IGF receptors. Since [125I]IGF-I binds to both type I and type II receptors in BC3H-1 cells, and since type I receptors have a higher affinity for IGF-I, the selective down-regulation of type I IGF receptors results in an apparent decrease in affinity for IGF-I. This difference in the regulation of type I and type II receptors in BC3H-1 myocytes is consistent with observations in other systems in which only one IGF receptor was present or examined. In their ability to be down-regulated by IGFs and insulin, type I IGF receptors are more similar to the structurally homologous insulin receptors than to the structurally dissimilar type II IGF receptors. These findings indicate that the BC3H-1 cell line provides an excellent model system in which to study the structure-function relationships of the receptor and effector pathways for insulin and the IGFs.

The relative contributions of type I and type II insulinlike growth factor (IGF) receptors and IGF carrier proteins to the binding of IGF-I tracer to cultured human fibroblasts were determined in competitive binding experiments that used unlabeled insulin and synthetic insulin-IGF-I hybrid molecules containing the A chain of insulin and the B domain of IGF-I. Whereas insulin binds only to type I IGF receptors, the B-IGF-I hybrids bind to type I receptors and IGF carrier proteins but not to type II receptors. In suspended human fibroblasts, IGF-I tracer binds predominantly to type I IGF receptors (inhibition by IGF-I much greater than insulin greater than B-IGF-I hybrid molecules). By contrast, in fibroblast monolayers, IGF-I binding was minimally inhibited by insulin or hybrid molecules, suggesting predominant binding to the type II IGF receptor. The type I receptor appears to be masked on fibroblast monolayers, and to require suspension or detergent solubilization of the cells to be demonstrated. In the course of the monolayers binding experiments, we noted that low concentrations of unlabeled IGF-I (5-10 ng/ml) or B-IGF-I hybrids (100 ng/ml) paradoxically increased IGF-I tracer binding up to twofold. We postulated that during the binding incubation (5 h, 15 degrees C), IGF-I tracer partitioned between binding sites on the cell surface and IGF carrier proteins released to the incubation media. Preferential occupancy of binding sites in the media by unlabeled ligand increased the tracer available to bind to the cells. In support of this hypothesis, carrier proteins were demonstrated in the media at the end of the binding incubation with fibroblast monolayers, and the concentration of unsaturated binding sites in the media correlated inversely with tracer binding to the cells. Thus carrier proteins released to the media during the binding incubation modulate the binding of IGF-I tracer to cell receptors, suggesting that the carrier proteins may play an important role in regulating cellular responsiveness to the IGFs.

Fanconi's anaemia is reported in 2 siblings. The simultaneous onset of pancytopenia after possible exposure to common external agents suggest that both a frail genotype and environmental factors may be etiologically involved in the disorder. One of the children died after having developed a monoblastic leukaemia. This patient disclosed very striking cytological abnormalities, including a dyserythropoietic pattern and ropalocytosis. The physiopathology of the latter abnormality, which has hitherto not been noticed in Fanconi's anaemia, is uncertain.

There are two types of insulin-like growth factor (IGF) receptors. The type I receptor generally binds IGF-I more tightly than IGF-II and also interacts weakly with insulin. The type II receptor prefers IGF-II over IGF-I and does not recognize insulin. The type I receptor is made up of an alpha binding subunit (Mr 130 000) and a beta subunit (Mr 95 000) probably organized as a heterotetramer (alpha 2 beta 2). The type II receptor consists of a single binding unit (Mr 250 000). IGF stimulates phosphorylation of the beta subunit of the type I receptor in whole cells and solubilized receptor preparations. Tyrosine kinase activity is associated with the type I receptor, resulting in autophosphorylation of the beta subunit and phosphorylation of exogenous substrates. In contrast, phosphorylation of the type II receptor in whole cells is less IGF-dependent, solubilized receptor preparations are not phosphorylated, and purified type II receptors do not exhibit tyrosine kinase activity toward the artificial substrate poly(Glu, Tyr)4:1. There are many similarities between the type I IGF receptor and the insulin receptor; however, different ligand-binding properties, subtle differences in the size of alpha and beta subunits, and immunoreactivity toward anti-receptor antibodies allow us to distinguish between these two receptors. The presence of both IGF receptors as well as insulin receptors on most cells and cross-reactivity of ligands for binding to these receptors present difficulties in assigning a particular biological response to a specific receptor. The type I receptor is down-regulated by ligand while in several cell types the type II receptor is rapidly up-regulated by insulin; the mechanism of up-regulation appears to be a translocation of type II receptors to the cell surface. There are two classes of serum binding proteins for IGF, a Mr 150 000 species found in adult blood and a Mr 40 000 species, which predominates in foetal blood. Like the type II receptor, IGF binding proteins do not bind insulin. The binding site on the type II receptor can be distinguished from the binding protein sites by a hybrid molecule Ainsulin-BIGF-I, which recognizes the binding protein but not the type II receptor. Binding proteins produced by cells in culture may cause confusion in the interpretation of experiments that are designed to study the binding of radiolabelled IGF to cell surface receptors in monolayer culture.

Plasma somatostatin immunoreactivity (SIR) was elevated 40-fold in an insulin-treated diabetic with disseminated pancreatic carcinoma. The diagnosis of somatostatinoma was supported by histological and ultrastructural similarities between metastatic cells and pancreatic D cells. Under acid conditions, 75% of the plasma SIR eluted as a 6000- to 7000-dalton protein and 25% as synthetic somatostatin (mol wt 1600), whereas the 20-fold elevated urine SIR consisted almost exclusively of the higher molecular weight fraction. The hypersomatostatinemia was associated with reduced basal and stimulated pancreatic hormone levels, which might reflect its involvement in the steatorrhea and diabetes, and its protection against ketoacidosis. Plasma SIR rose 50% upon insulin withdrawal and 10-fold after tolbutamide injection and fell 30% after diazoxide. It is concluded that an increase in plasma and urine SIR, the presence of a 6000- to 7000-dalton SIR fraction in plasma and urine, a reduction in basal and stimulated pancreatic hormone levels, and tolbutamide-induced somatostatin release can be diagnostic for a somatostatinoma. Streptozotocin reduced tumor volume, hypersomatostatinemia, and tolbutamide-induced somatostatin release, suggesting that this drug may be useful in the treatment of disseminated somatostatinoma.

The insulin-like growth factors (IGFs) are polypeptides in plasma that are chemically related to insulin and have mitogenic and insulin-like activity. Unlike insulin, the IGFs circulate in plasma bound to specific high molecular weight carrier proteins that regulate their delivery to target tissues. To define the sites on the IGFs that allow them to be recognized by carrier proteins, we constructed hybrid molecules containing different portions of the insulin, IGF-I, and IGF-II molecules. The presence of the B domain of IGF-I, but not the D domain of IGF-II, enables these insulin-IGF hybrid molecules to be recognized by acid-stripped IGF carrier proteins from rat serum and other sources. By contrast, neither the BIGF-I nor DIGF-II domain is sufficient to enable binding to type II IGF receptors, despite the fact that type II receptors, like the carrier protein, specifically bind IGF-I and IGF-II but do not interact with insulin. By differentiating those sites on the IGF molecule required for binding to IGF carrier protein and receptors, the insulin-IGF hybrid molecules should help delineate the role of the carrier protein in presenting biologically active IGF to target tissues.

Primary cortisol resistance in man is a familial disease characterized by increased plasma cortisol concentrations, high urinary free cortisol excretion, a normal circadian pattern of cortisol secretion, resistance to adrenal suppression by dexamethasone and absence of the clinical stigmata of Cushing's syndrome or signs of adrenal insufficiency. In its severe form, hypertension and hypokalemic alkalosis are present, owing to increased secretion of the sodium-retaining corticoids, corticosterone and deoxycorticosterone. In subjects with a less severe resistance to cortisol, there are no clinical abnormalities and the disease is revealed only by detailed examination of several parameters of cortisol metabolism or by glucocorticoid receptor studies. In whole-cell glucocorticoid receptor assays (peripheral mononuclear leukocytes, fibroblasts, or B-lymphocytes transformed with the Epstein-Barr Virus) low receptor affinity for dexamethasone could be demonstrated conclusively only in the severely affected subject. When affected cells are transformed with the Epstein-Barr virus, receptor induction is less than that of normal cells. The decreased affinity of the receptor for its ligand is reflected in an increased rate of loss of specific bound ligand during thermal activation. The molecular weight of the receptor, determined by SDS-PAGE, is similar to that from normal cells (approximately 92,000). Only in the severely affected patient was the proportion of activated receptor remaining in the cytosol of thermally activated intact cells reduced. At saturating concentrations of dexamethasone, nuclear binding appears normal in cells from both the severe and the asymptomatic forms of this condition, providing an explanation for the apparently complete compensation of the target tissue resistance to glucocorticoids by the high plasma cortisol levels. The clinical manifestations of the disorder (hypertension, hypokalemia) can be corrected with high doses of dexamethasone (3mg/day).

Peripheral levels of basal and tolbutamide-induced somatostatin have been measured in patients with diabetes or impaired glucose tolerance (IGT) and compared with those in normal individuals. Basal somatostatin was significantly higher in patients with Type 1 diabetes than in age-matched control subjects. This increase was most pronounced at diagnosis, and appeared to be related to metabolic control in insulin-treated patients. No increase was noted in patients with Type 2 diabetes or with IGT. Intravenous bolus injection of tolbutamide enhanced peripheral somatostatin levels in healthy volunteers in a biphasic manner. Patients with IGT also exhibited a biphasic response but the amplitude of the first phase was higher. No secretory response was detected in 27/29 Type 1 diabetic patients at diagnosis; a somatostatin response to tolbutamide became detectable again in Type 1 patients with normalization of their basal somatostatin levels but was then paradoxically related to poor blood glucose control. In Type 2 diabetes, basal somatostatin levels were similar to age-matched control subjects, but decreased upon intravenous tolbutamide administration.

In order to ascertain the first vascular lesions responsible for juvenile diabetic retinopathy, 408 fluorescein angiographies were performed in 114 diabetic children and adolescents whose diabetes became clinically apparent before the age of 14 years. Compared with regular ophthalmoscopy, fluorescein angiography doubles the frequency of the diagnosis of incipient retinopathy. In addition to the classical diabetic lesions, fluorescein leakages are demonstrated in 50% of diabetic eyes with initial retinopathy. They probably reflect early changes in capillary permeability. They appear often before microaneurysms. Duration of diabetes as well as insufficient and poor metabolic control considerably increase the frequency of retinopathy.