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Objectives: Post-hoc analyses have shown an increase incidence of fractures among type 2 diabetes (T2DM) patients treated with thiazolidinediones (TZDs). The mechanisms by which TZDs may be associated with increased fracture risk is not well understood. This article describes the study design and baseline characteristics for a prospective, randomized, double-blind, active-controlled trial to evaluate the effects of rosiglitazone on changes in measures of skeletal structure, surrogates of bone strength and metabolism., Methods: Postmenopausal women without osteoporosis and diagnosed with T2DM were randomized in a double-blind design to either rosiglitazone or metformin for 52 weeks, then all subjects received open-label metformin for 24 weeks. Study endpoints included changes in bone mineral density (BMD), quantitative computed tomography (QCT), digitized hip radiography (HXR) and high resolution magnetic resonance imaging (hrMRI). Serum markers of bone metabolism and indices of glycemic control were assessed within and between treatment groups., Results: A total of 226 subjects were randomized. Baseline characteristics included: age 63.8 ± 6.5 years; years postmenopausal 16.9 ± 8.4; duration of diabetes 3.5 (1.8-7.8) years; body mass index (BMI) 31.4 ± 5.9 kg/m(2); and glycated hemoglobin (HbA1c) 6.4 ± 0.65%. At baseline, mean T-scores were -0.95 ± 0.91 at the femoral neck, -0.02 ± 0.97 at the total hip and -0.55 ± 1.25 at the total spine. Since there are no well recognized techniques to determine bone mass and structure at the distal limbs (cortical bone sites where fractures were reported in RSG subjects), using the femoral neck as a surrogate for these areas may be a potential limitation of the study., Conclusion: This is the first randomized trial utilizing multiple techniques to evaluate bone mass, structure, serum markers of bone remodeling, and potential reversibility of changes after discontinuation of rosiglitazone. This study will provide information about RSG bone effects in a population of postmenopausal women at risk for bone loss and subsequent fracture., Clinicaltrialsgov Number: NCT00679939.

Background: Oral bisphosphonates comprise the most widely prescribed class of antiosteoporotic drugs. Recent reports, however, propose a link between prolonged bisphosphonate use and atypical, low-energy, subtrochanteric fractures., Objectives: The aim was to describe the clinical course of a patient treated long-term with alendronate who developed subtrochanteric stress fractures and to propose a hypothesis to explain teriparatide's potential contribution in healing the patient's stress fractures., Results: Magnetic resonance imaging (MRI) showed classical bilateral stress fractures of the mid-femora. Baseline serum 25-hydroxyvitamin D(3) was low; bone-specific alkaline phosphatase was slightly increased; serum carboxyterminal cross-linking telopeptide of bone collagen and urine aminoterminal cross-linking telopeptide of bone collagen were low to normal, as was serum osteocalcin. Dual-energy x-ray absorptiometry showed osteopenic vertebral bone mineral density and osteoporotic hip values. Treatment with large doses of oral vitamin D increased serum 25-hydroxyvitamin D(3) to normal within 2 months, after which it remained in the normal range with maintenance doses. Thigh pain, present as an initial symptom, intensified, and the MRI appearance of the fractures worsened. Teriparatide treatment commenced, and 6 months later, a repeat MRI showed decreased edema at the fracture sites with faint cortical bridging. Thigh pain and lower limb weakness disappeared over the next year, and complete fracture healing was established (MRI)., Conclusions: Based upon the chronology of fracture healing in our patient and published evidence that teriparatide heals stress fractures in a rat model, we think that teriparatide was probably primary in this patient's positive response to therapy, with calcium, vitamin D therapy, and alendronate discontinuation playing secondary roles.

Daily treatment with hPTH (1-34) is associated with a significant increase in bone formation which results in large gains in lumbar spine bone mass. However, bone formation is known to occur on trabecular, endocortical and periosteal surfaces. The purpose of this study was to determine whether daily treatment with hPTH (1-34) for 1 year was associated with a change in vertebral cross-sectional area, or vertebral size, as measured by serial quantitative computed tomography scans. Fifty-one postmenopausal women treated chronically with both glucocorticoids and hormone replacement therapy (HRT) were randomized to either daily hPTH (1-34) for 1 year and HRT or to a control group treated with only HRT. Measurements of bone density of the spine were obtained every 6 months by dual-energy X-ray absorptiometry (DXA) and annually by QCT of the L1 and L2 vertebrae. Vertebral cross-sectional area (VCSA) was obtained from the QCT scans. In addition, we estimated the vertebral compressive strength (VSFOM, g(2)/cm(4) = trabecular BMD(2) x VCSA). After 1 year of hPTH (1-34) treatment, VCSA increased 4.8% (p < 0.001), and 1 year after treatment was discontinued VCSA was still 2.6% higher than the baseline value (p < 0.05). The control group had no change in VCSA. In addition, estimated vertebral compressive strength increased more than 200% over baseline levels in the hPTH (1-34) treatment group and no change was observed in the control group. In summary, daily treatment with hPTH (1-34) for 1 year increased vertebral size as measured by VCSA and this increase was maintained after hPTH (1-34) was discontinued. Since vertebral fracture risk is related to both bone size and bone mass, we cautiously speculate that the increase in vertebral size associated with hPTH (1-34) treatment is at least partially responsible for increased vertebral bone strength and reduction of fracture risk associated with this therapy in postmenopausal osteoporosis.

Glucocorticoid-induced osteoporosis is the most common secondary cause of osteoporosis. In this 24-month study, we report changes in bone turnover and bone mass after 12 months of daily injections of human parathyroid hormone 1-34 [hPTH(1-34)] and 12 months off treatment in postmenopausal women (mean age, 63 years) with osteoporosis treated with glucocorticoid and hormone replacement therapy. Response to the treatment was assessed with bone mineral density (BMD) measurements of the lumbar spine by quantitative computed tomography (QCT); BMD measurements of the lumbar spine, hip, and forearm by dual-energy X-ray absorptiometry (DXA); and biochemical markers of bone turnover. The mean (+/-SEM) change in BMD of the lumbar spine by QCT and DXA in the PTH group at 24 months was 45.9+/-6.4% and 12.6+/-2.2% (p < 0.001). The change in total hip and femoral neck BMD was not significant at 12 months but increased to 4.7+/-0.9% (p < 0.01) and 5.2+/-1.3% at 24 months, respectively, as compared with a relatively small change of 1.3+/-0.9% and 2.6+/-1.7% in the estrogen-only group. The mean percent differences in BMD of the lumbar spine by QCT and DXA between the groups at 24 months were 43.1% and 11.9%, respectively (p < 0.001). The mean percent differences over the estrogen-only group in hip BMD were 3.4% for total hip (p < 0.01) and 2.6% for femoral neck at 24 months. Biochemical markers of bone turnover increased to more than 150% during the first 6 months of therapy, remained elevated throughout the 12-month treatment period, and returned to baseline values within 6 months of discontinuing the PTH treatment. These results suggest that PTH dramatically increases bone mass in the lumbar spine and hip in postmenopausal women with glucocorticoid-induced osteoporosis who are taking hormone replacement therapy. However, the maximum effect of this anabolic agent on bone mass at the hip after 12 months of treatment requires at least 6-12 months after the PTH treatment is discontinued.

Rodent models suggest that estradiol deficiency promotes bone loss through increasing interleukin-6 (IL-6) activity. However, it is controversial as to whether these findings are applicable to humans. To evaluate estradiol-mediated modulation of IL-6 activity in relation to bone metabolism in humans, we measured serum IL-6, soluble interleukin-6 receptor (sIL-6R), estradiol (E2), progesterone, luteinizing hormone, follicle-stimulating hormone, intact parathyroid hormone (PTH), serum and urine Ca, and bone biochemical markers (serum bone-specific alkaline phosphatase, osteocalcin, and serum and urine deoxypyridinoline [Dpd]) across one menstrual cycle for 211 women. Neither IL-6 nor sIL-6R levels differed between the follicular phase (FP) and the luteal phases (LP). However, IL-6 was negatively correlated with E2 during the FP (p =0.003). Furthermore, IL-6 correlated positively with serum Ca over the entire cycle (p = 0.0091. Serum Ca correlated positively with serum (p = 0.040) and urine (p = 0.006) Dpd. PTH was significantly higher during the FP than in the LP (p = 0.004). PTH was negatively related to E2 (p = 0.002), serum Ca (p < 0.001), and urine Ca (p = 0.036), whereas it was positively correlated with IL-6 (p = 0.027). These data demonstrate that IL-6 and PTH fluctuate with E2, and serum II-6 is associated with PTH levels during the menstrual cycle. However, the role of 11-6 in bone remodeling during the normal menstrual cycle remains to be determined.

The purpose of this study was to test the ability of early changes in markers of bone turnover to predict subsequent changes in bone mineral density (BMD) induced by parathyroid hormone fragment, PTH (1-34), in postmenopausal osteoporotic women treated with estrogen and glucocorticoids. Forty-nine postmenopausal women with chronic, inflammatory diseases and BMD T-scores < or = -2.5 at the lumbar spine or femoral neck who were concurrently treated with estrogen > or = 1 year and prednisone 5-20 mg/day for > or = 1 year participated. Subjects were randomized to treatment with human PTH (1-34) 400 IU/day or to a control group for 1 year and followed for an additional year. Serum and urine were collected at baseline and 1, 3, 6, 9, 12, 18 and 24 months for measurement of bone alkaline phosphatase (BAP), osteocalcin (OC) and deoxypyridinoline (DPD). We constructed an Uncoupling Index (UI) from all three markers (UI = [ZBAP + Zoc]/2 -ZDPD, where the Z-score for each marker in each subject was calculated from the mean and standard deviation of the study population at baseline). BMD of the lumbar spine and hip was measured at baseline and every 6 months thereafter by dual-energy X-ray absorptiometry (DXA) and annually by quantitative computed tomography (QCT; spine only). BMD of the spine, but not hip (total, femoral neck or trochanter), and levels of all three markers increased significantly as a result of PTH treatment (p<0.01 compared with controls). The resorption response lagged behind that of formation as evidenced by a significant increase (p < 0.05) in the UI for the first 9 months of treatment. The UI values and changes from baseline to 1, 3 and 6 months in BAP, OC and DPD were correlated with the 12- and 24-month changes in spine BMD measured both with QCT and with DXA (Spearman's rank coefficients <0.76; p<0.05). Most PTH-treated subjects could be identified as biochemical responders by least significant change analysis. Following 1 month of therapy, BAP and OC identified 65% and 81% as responders, respectively. The responder rates were 79%, 79% and 75% for BAP, OC and DPD, respectively by 6 months. Responders exhibited a high level of diagnostic accuracy for predicting a gain in BMD (areas under the receiver operating characteristic curves exceeding 0.79 for QCT and 0.70 for DXA), but not the magnitude of the gain. These data suggest that serial bone marker measurements may be useful in identifying skeletal responders to an anabolic therapy, such as PTH, in estrogen-replete postmenopausal women with glucocorticoid-induced osteoporosis.

SERMs are a class of drugs with mixed estrogen agonist/antagonist effects that have great potential at targeting changes seen in the postmenopausal period. Raloxifene is effective in preventing bone loss and may prevent fractures in postmenopausal osteoporosis. It induces changes in lipoprotein concentrations that should be cardioprotective. It has no stimulatory effect on the uterus and is well tolerated. Raloxifene is an attractive alternative to HRT in preventing postmenopausal bone loss, especially for women that are more concerned about the risk of breast cancer or vaginal bleeding. Unanswered questions include raloxifene's effect on fracture incidence, cardiac events, and dementia; long-term safety data are also needed. Its potential role in the primary prevention of breast cancer also needs large, long-term studies. Tamoxifen has been used traditionally as adjuvant therapy for breast cancer, but new data indicate that it is effective in the primary prevention of breast cancer in women at increased risk. Its effects on bone and lipoproteins are attractive complementary effects when used in the subset of women at increased risk for breast cancer. New generations of SERMs are being developed that may have more potent estrogen agonist effects on bone and cardiovascular disease, or more potent antiestrogen effects, especially at the breast. There will likely be a selection of SERMs available, and the choice of SERM for a woman will be tailored to her specific issues and risk profile.

To examine the ability of commercially available biochemical markers of bone formation and resorption to predict hip bone loss, we prospectively obtained serum and timed 2-h urine specimens from 295 women age 67 years or older who were not receiving estrogen replacement therapy. Serum was assayed for two markers of bone formation: osteocalcin (OC) and bone-specific alkaline phosphatase (BALP). Urine specimens were assayed for four markers of bone resorption: N-telopeptides (NTX), free pyridinolines (Pyr), free deoxypyridinoline (Dpyr), and C-telopeptides (CTX). Measurements of hip bone mineral density were made at the time the samples were collected and then repeated an average of 3.8 years later. Higher levels of all four resorption markers were, on average, significantly associated with faster rates of bone loss at the total hip, but not at the femoral neck. Women with OC levels above the median had a significantly faster rate of bone loss than women with levels below the median, but there was no significant association between levels of BALP and hip bone loss. The sensitivity and specificity of higher marker levels for predicting rapid hip bone loss was limited, and there was considerable overlap in bone loss rates between women with high and low marker levels. We conclude that higher levels of urine NTX, CTX, Pyr, Dpyr, and serum OC are associated with faster bone loss at the hip in this population of elderly women not receiving estrogen replacement therapy, but these biochemical markers have limited value for predicting rapid hip bone loss in individuals.

To determine if the cyclic changes of female sex hormones during the menstrual cycle are related to changes in bone formation and resorption, we measured serum bone-specific alkaline phosphatase (BAP) and osteocalcin (OC) and bone resorption markers, serum and urine deoxypyridinoline (Dpyr), three times per week during one menstrual cycle in 20 healthy premenopausal women. Serum estradiol (E2) and progesterone (P) showed characteristic cyclic fluctuations. Serum Dpyr was higher during the follicular phase (FP) than in the luteal phase (p = 0.027). Serum BAP, OC, and urine Dpyr levels did not change substantially across the cycle. Serum Dpyr correlated negatively with serum E2 values measured 6 (p = 0.011) and 8 (p = 0.001) days earlier and with P measured concurrently (p = 0.033) 2 (p = 0.002), 4 (p = 0.003), and 6 (p = 0.014) days earlier. BAP correlated negatively with E2 measured 6 days earlier (p = 0.006). We found no statistically significant correlations of E2 or P with OC or urine Dpyr within women over their cycles. BAP was positively correlated with concurrent serum Dpyr (p = 0.015) during the menstrual cycle. Serum OC levels correlated inversely with age (rs = -0.48, p = 0.036). Women with higher mean urine Dpyr levels had higher mean serum OC levels (rs = 0.49, p = 0.033) and showed a trend toward lower hip bone mineral density (rs = -0.40, p = 0.078). We conclude that the low level of E2 and/or P observed during the FP of the normal menstrual cycle is associated with increased bone resorption. These relationships suggest that normal women experience monthly episodes of increased bone resorption from menarche to menopause.

Various derivatives of human calcitonin have been synthesized and their biological characteristics compared with those of existing calcitonins. The acute effects of these analogues in reducing serum calcium levels and suppressing appetite were assessed in rats. A calcitonin analogue, PO-1 (CGNLSTCMLGKLSQELHKLQTYPQTAIGVGAP-NH2), having both the N- and C-terminal ten amino acid sequences those of human calcitonin, and the 12 amino acid central region that of salmon calcitonin, was found to have equal effectiveness with salmon calcitonin and elcatonin for reducing serum calcium levels. Strong hypocalcemic activity was also exhibited by PO-23 ([cyclo-Asp1, Lys7]-[des-Gly2]-[Leu8]-PO-1) and PO-29 ([Asp15, Asn17 , Phe19, His20]-PO-23). PO-23 was prepared by replacing the N-terminal Cys-Cys S-S bond of PO-1 with a ring structure composed of an Asp-Lys peptide bond to enhance physicochemical stability. PO-29 was prepared by modifying the central area of the PO-23 molecule to more closely mimic human calcitonin. When tested in vitro, human calcitonin analogues with a [cyclo-Asp1, Lys7] structure showed biological activities on osteoclast-like cells comparable to those of existing calcitonins (salmon calcitonin and elcatonin) in keeping with their relative potencies for in vivo hypocalcemic action. Acute anorectic activity in rats was strong with salmon calcitonin and elcatonin but relatively reduced with human calcitonin analogues having a [cyclo-Asp1, Lys7] structure. The activities of these analogues on kidney cells were also weaker than that of salmon calcitonin or elcatonin. These results suggest that stable human calcitonin analogues with a [cyclo-Asp1, Lys7] structure suppress bone resorption to a degree similar to that of salmon calcitonin or elcatonin with weaker activities on non-osseous tissues which might be related to adverse reaction.

Corticosteroid-induced osteoporosis is the most common secondary cause of osteoporosis. We conducted a 12-mo, randomized clinical trial of human parathyroid hormone 1-34 (hPTH 1-34) in postmenopausal women (mean age was 63 yr) with osteoporosis who were taking corticosteroids and hormone replacement therapy. Response to the treatment was assessed with bone mineral density (BMD) measurements of the lumbar spine by quantitative computed tomography (QCT); BMD measurements of the lumbar spine, hip, and forearm by dual-energy x-ray absorptiometry (DXA); and biochemical markers of bone turnover. The mean (+/-SE) changes in BMD of the lumbar spine by QCT and DXA in the PTH group were 35+/-5.5% and 11+/-1.4%, respectively, compared with a relatively small change of 1.7+/-1.8% and 0+/-0.9% in the estrogen-only group. The differences in mean percentage between the groups at 1 yr were 33.5% for the lumbar spine by QCT (P < 0.001) and 9.8% for the lumbar spine by DXA (P < 0.001). The changes in the hip and forearm were not significantly different between or within the groups. During the first 3 mo of PTH treatment, markers of bone formation increased to nearly 150%, whereas markers of bone resorption increased only 100%, suggesting an early uncoupling of bone turnover in favor of formation. These results suggest that parathyroid hormone dramatically increases bone mass in the central skeleton of postmenopausal women with corticosteroid- induced osteoporosis who are taking hormone replacement.

Chronic steroid use results in osteoporosis, and postmenopausal women are believed to be at a high risk for steroid-induced bone loss. The purpose of this study was to determine predictors of bone mineral density (BMD) in postmenopausal women on both chronic steroid and hormone replacement therapy. Seventy-six postmenopausal women (> or = 3 years postmenopausal, > or = 2 years of steroid treatment of > or = 5 mg/day of prednisone, and > or 1 year of hormone replacement therapy) were recruited into this study. Measurements of BMD of the lumbar spine and femoral neck were obtained in all subjects. Risk factors for osteoporosis were obtained by questionnaire. Discriminant analysis was performed to determine predictors of BMD. Osteoporosis, defined by a T score of < -2.5, was present in the lumbar spine or femoral neck in 34 of the 76 subjects. Based on these criteria, women with osteoporosis were significantly older, were more years postmenopausal, and had a lower body mass index (BMI) than women who did not have osteoporosis. Predictors of osteoporosis for both the femoral neck and spine included a low BMI (P < 0.05), more years postmenopausal (P < 0.01), and more years on steroids (P < 0.01). Low BMI was the only significant predictor of osteoporosis in the lumbar spine (P < 0.05), whereas for the femoral neck both years on steroids (P < 0.05) and BMI (P < 0.05) were significant predictors of low BMD. In summary, not all postmenopausal women on chronic steroid and hormone replacement therapy are osteoporotic but a low BMI, more years on steroids, and more years postmenopausal were significant predictors of osteoporosis in these subjects.

Objective: Our purpose was to determine the characteristics of menopause among Mayan women who did not have menopausal symptoms., Study Design: A cross-sectional study of Mayan women from Chichimila, Mexico, was performed. Demographic information, history and physical examination, hormone concentrations, and radial bone density measurement were obtained., Results: Fifty-two postmenopausal women were compared with 26 premenopausal women. Menopause occurred at 44.3 +/- 4.4 years. None of the women admitted to hot flushes and did not recall significant menopausal symptoms. Hormone levels included elevated follicle-stimulating hormone (66.6 +/- 29 mlU/ml), low estradiol and estrone (9.4 +/- 8.3 and 13.3 +/- 7.8 pg/ml), estrone greater than estradiol levels, normal levels of testosterone and androstenedione (0.17 +/- 0.14 and 0.31 +/- 0.17 ng/ml). Bone mineral density declined with age, but height did not. Clinical evidence of osteoporosis was not detected., Conclusions: Lack of symptoms during the menopausal transition is not attributable to a difference in endocrinology. Postmenopausal Mayan women are estrogen deprived and experience age-related bone demineralization but do not have a high incidence of osteoporotic fractures.

Estrogen deficiency is the major determinant of increased bone resorption and bone loss occurring in early menopause (first 5-6 years). The increased bone resorption is probably caused by the release of immune system cytokines such as IL-1, IL-6 and TNF by osteoblasts, the biosynthesis of which is no longer suppressed by estrogen. PTH secretion, although decreased in early menopause, may also contribute to increased bone destruction because of the presence of cytokines such as IL-1 and TNF which increase the sensitivity of bone to the resorptive effects of PTH. For the same reasons, the bone-destructive effects of increased serum levels of PTH occurring in the late menopause may be exaggerated.

The frizzled (fz) locus of Drosophila encodes a protein (Fz) with a seven-transmembrane-domain profile characteristic of G-protein-coupled receptors. In Drosophila, genetic evidence suggests that Fz functions to transmit and transduce polarity signals in epidermal cells during hair and bristle development. We have isolated from a UMR 106 rat osteosarcoma cell library a cDNA (fz-1) encoding a predicted 641-residue protein (Fz-1) with 46% homology with Drosophila Fz. We also identified a second cDNA (fz-2) encoding a protein (Fz-2) of 570 amino acids that is 80% homologous with Fz-1, with divergence most evident in the extracellular domains. Southern blots of rat genomic DNA indicated that fz-1 and fz-2 represent distinct genes. Northern analysis revealed the presence of a single fz-1 mRNA (4.7 kilobases) and two fz-2 mRNAs (2.5 and 4.5 kilobases) in rat tissues. The fz-1 and fz-2 genes are widely expressed in rat tissues with the highest steady-state levels of mRNA in kidney, liver, heart, uterus, and ovary. fz-1 and -2 mRNA levels were greater in neonatal than in corresponding adult tissues. Treatment of UMR 106 cells with bone resorbing agents including parathyroid hormone, epidermal growth factor, and 1,25-dihydroxyvitamin D3 produced increases in fz-1 and -2 mRNA levels. We suggest that hormonal induction of Fz proteins in osteoblasts serves to promote intercellular signaling required for functional responses such as increased bone resorption. Fz-1 and Fz-2 may represent products of a gene family whose members serve as transducers or intercellular transmitters of signals required for normal morphogenesis and/or differentiated function in diverse tissues.

Administration of excessive amounts of parathyroid hormone (PTH) in the treatment of osteoporosis can reverse the beneficial effects of a low-dose, intermittent regime. To investigate the direct actions and the possible cellular mechanisms of PTH in inducing desensitization of PTH receptors, we studied the effects of desensitization on rat osteoblastic UMR-106 cells. When the osteoblasts were preincubated with bPTH-(1-34), complete refractoriness to a subsequent challenge with the hormone developed within 1 h and at hormone concentrations as low as 5 nM. When osteoblasts thus desensitized were incubated in hormone-free medium, recovery of the cAMP responses began within 2 h and reached maximum after 16 h. Cycloheximide did not affect the process of desensitization. [Nle8,Nle18,Tyr34]bPTH-(3-34)amide significantly impaired the desensitization process by PTH-(1-34) but did not have stimulatory effect on cAMP responses. No significant heterologous desensitization was obvious after preincubation with isoprenaline (50 microM), prostaglandin E1 (50 microM), or prostaglandin E2 (50 microM) for 2 h. Binding experiments with [125I]PLP-(1-36)amide after desensitization revealed that there was an approximate twofold decrease in receptor affinities as analyzed by Scatchard analysis, showing that the decrease in affinity was prominent in the process of desensitization. When the cells were treated with monensin during desensitization, PTH challenge after desensitization produced significantly lower cyclic AMP responses. Recovery after desensitization occurred over a period of 16 h. Inclusion of monensin, but not cycloheximide, impaired the recovery. The results show that homologous desensitization of rat osteoblasts to PTH is brought about by the occupancy of receptors by PTH-(1-34) but not by cAMP generation itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium requirements may vary throughout the lifespan. During the growth years and up to age 25-30, it is important to maximize dietary intake of calcium to maintain positive calcium balance and achieve peak bone mass, thereby possibly decreasing the risk of fracture when bone is subsequently lost. The RDA for age 10-25 is 1200 mg/day. Calcium intake need not be greater than 800 mg/day during the relatively short period of time between the end of bone building and the onset of bone loss (30 to 40 years old). Starting at age 40-45, both men and women lose bone slowly, but women lose bone more rapidly around the menopause and for about 10 years after. Intestinal calcium absorption and the ability to adapt to low calcium diets are impaired in many postmenopausal women and elderly persons owing to a suspected functional or absolute decrease in the ability of the kidney to produce 1,25(OH)2D3. The bones then become more and more a source of calcium to maintain critical extracellular fluid calcium levels. Available evidence suggests that the impairments of intestinal calcium absorption observed during the menopause and aging can be overcome only by inordinately large calcium intakes (1500 to 2500 mg/day). Since this amount is difficult to derive from the diet, can cause constipation, and may not prevent trabecular bone loss, it should not be used as a substitute for sex hormone replacement. Women taking estrogen replacement should be provided the RDA for calcium of 800 mg/day at a minimum. Those who cannot or will not take estrogen should be asked to ingest at least 1000 to 1500 mg/day of calcium to delay cortical bone loss and prevent secondary hyperparathyroidism. It should be emphasized that up to 2000 mg/day of calcium is safe in teenaged children and adults. Excessive dietary intake of protein and fiber may induce significant negative calcium balance and thus increase dietary calcium requirements. It is also possible that excessive intakes of phosphate could have a deleterious effect on calcium balance in populations whose need for calcium is great (e.g. growing children) or whose ability to produce 1,25(OH)2D3 is impaired (e.g. the elderly). Moderation in the intake of these nutrients is urged. Generally, the strongest risk factors for osteoporosis are uncontrollable (e.g. sex, age, and race) or less controllable (e.g. disease and medications). However, several factors such as diet, physical activity, cigarette smoking, and alcohol use are lifestyle related and can be modified to help reduce the risk of osteoporosis.

Study Objective: To measure the serum levels of a newly described parathyroid hormone-like protein (PLP) which was isolated from malignant tumors associated with hypercalcemia, and determine whether PLP is a humoral factor in malignancy-associated hypercalcemia., Design: A cross-sectional study of serum levels of PLP using a newly developed radioimmunoassay., Setting: A university-affiliated Veterans Administration hospital in San Francisco, California, a University hospital in Hong Kong, and a private hospital in Danville, Pennsylvania., Patients: Patients with hypercalcemia (calcium greater than 2.65 mmol/L) and a diagnosis of malignancy were studied. Control groups included normocalcemic patients with malignancy, patients with hyperparathyroidism, and normal subjects., Measurements and Main Results: Serum immunoreactive PLP (iPLP) levels in normal subjects were less than 2.5 pmol eq/L (10 pg/mL), and 68% of subjects had undetectable levels. The serum concentration of iPLP was normal in 15 of 16 hypercalcemic patients with hyperparathyroidism. Serum iPLP was increased (greater than 2.5 pmol eq/L) in 36 of 65 (55%) patients with malignancy-associated hypercalcemia, with a mean value of 6.1 +/- 0.9 pmol eq/L (24 pg/mL). In a subgroup of patients with solid tumors serum iPLP was increased in 30 (71%) of 42 hypercalcemic patients, with a mean value of 6.5 +/- 0.9 pmol eq/L. Serum iPLP was elevated in only 3 of 23 normocalcemic patients with cancer. In patients with solid malignancies (n = 59), levels of iPLP were positively correlated with the total serum calcium (r = 0.43, P less than 0.01)., Conclusion: The data indicate a relation between the serum concentration of iPLP and the presence of hypercalcemia in solid malignancies. The results support a role for PLP as a humoral mediator of hypercalcemia in most patients with solid tumors. Measurement of iPLP should be useful in the differential diagnosis of hypercalcemia.

We have demonstrated binding of synthetic bovine parathyroid hormone (1-34) [bPTH-(1-34)] to embryonic avian bone cells in monolayer culture. The binding sites have qualitative and quantitative characteristics of a physiologically important parathyroid hormone (PTH) receptor. At apparent steady state (60 min at 24 degrees C), 5-10% of electrolytically labeled, receptor-purified 125I-labeled bPTH-(1-34) bound specifically to the cells whereas nonspecific binding was less than 1% of the added labeled hormone. Scatchard analysis showed a single order of PTH binding sites (Kd = 0.6 nM) with approximately 10,000 sites per cell. In this bone cell system, PTH bound to its binding site and stimulated cAMP accumulation over the same concentration range. Bovine PTH-(1-84) bound to the cells with the same apparent affinity as bPTH-(1-34).

Putative parathyroid hormone (PTH) receptors in canine renal membranes were affinity labeled with 125I-bPTH(1-34) using the heterobifunctional cross-linking reagent N-hydroxysuccinimidyl 4-azidobenzoate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of a major 85,000 molecular weight (Mr) PTH binding component, the labeling of which was inhibited by nanomolar concentrations of unlabeled PTH and by micromolar concentrations of 5'-guanylyl imidodiphosphate [Gpp-(NH)p]. Labeling was not influenced by the unrelated peptides insulin and arginine vasopressin. Minor PTH binding components of Mr 55,000 and 130,000 were also seen, and labeling of these was likewise sensitive to unlabeled PTH and to Gpp(NH)p. Omission of protease inhibitors during the isolation of plasma membranes resulted in the loss of the Mr 85,000 PTH binding species and the appearance of an Mr 70,000 form. Several minor PTH binding components also were observed. Equilibrium binding studies showed that such membranes had an affinity for PTH indistinguishable from that in membranes isolated with protease inhibitors and displaying a major Mr 85,000 PTH binding species. We conclude that the major form of the adenylate cyclase coupled PTH receptor in canine renal membranes is an Mr 85,000 protein. An endogenous enzyme, probably a lysosomal cathepsin, can cleave this form to produce an Mr 70,000 receptor that retains full functional activity with respect to high-affinity, guanyl nucleotide sensitive PTH binding. The ability to covalently label the PTH receptor in high yield represents a major step toward the structural characterization of this important detector molecule.

The effect of phosphorus (inorganic phosphate) supplementation was studied in seven postmenopausal women with osteoporosis. Prior to supplementation, all chemical parameters studied in serum and urine were normal. Bone density was below the fifth percentile for age in all but one patient, and the percentage of bone surface involved in resorption was higher than normal. During administration of the phosphorus supplement, fasting serum concentrations of calcium and immunoreactive parathyroid hormone showed no significant changes, while serum phosphorus, urinary calcium, and tubular reabsorption of phosphorus decreased. In four patients studied by balance techniques, calcium balance became positive or less negative. Bone-forming surface decreased and bone-resorbing surface increased in all patients. Bone-resorbing surface was highly correlated with total phosphorus intake. Density of the distal radius changed variably, while density of the midradius increased slightly in all patients.

The purpose of this study was to determine whether plasma levels of the vitamin D hormone and parathyroid hormone (PTH), two potent activators of bone remodeling sites, were altered in four astronauts during the 8-day (d) Spacelab 2 mission (SL2). Increased circulating levels of either hormone could change calcium homeostasis and bone cell activity and, thus, contribute to bone loss in crewmembers in space. The vitamin D hormone was elevated in all astronauts at the end of the first inflight day but returned to normal by the seventh day. Biologically active PTH tended to be normal throughout the mission. Both hormones were within the normal range by the end of the 8-d flight of this SL2 crew. Plasma levels of 25OHD, 24,25(OH)2D, calcium, phosphorus, and albumin were essentially normal during the mission.

Exposure of cultured embryonic chicken bone cells to the PTH agonists bovine (b) PTH-(1-34) and [8Nle, 18Nle, 34Tyr]bPTH-(1-34)amide [bPTH-(1-34)A] reduces the subsequent cAMP response to the hormone and decreases the specific binding of 125I-labeled PTH to these cultures. To determine whether PTH receptor down-regulation in cultured bone cells is mediated by cellular internalization of PTH-receptor complexes, we measured the uptake of [125I]bPTH-(1-34) into an acid-resistant compartment. Uptake of radioactivity into this compartment was inhibited by incubating cells at 4 C with phenylarsineoxide and unlabeled bPTH-(1-34). Tracer uptake into the acid-resistant compartment at any time was directly proportional to total cell binding at 22 C. Thus, it is likely that PTH-receptor complexes are internalized by bone cells. This mechanism may explain the loss of cell surface receptors after PTH pretreatment. To determine whether internalized PTH-receptor complexes are reinserted into the plasma membrane, we measured PTH binding and PTH stimulation of cAMP production after cells were exposed to monensin, a known inhibitor of receptor recycling. Monensin (25 microM) had no effect on PTH receptor number or affinity and did not alter PTH-stimulated cAMP accumulation. However, monensin (25 microM) incubated with cells pretreated with various concentrations of bPTH-(1-34) for 1 h potentiated the effect of the hormone to reduce subsequent [125I]bPTH-(1-34) binding and PTH-stimulated cAMP accumulation by more than 2 orders of magnitude. Chloroquine also potentiated PTH-induced down-regulation of PTH receptors. By contrast, neither agent influenced PTH binding or PTH-stimulated cAMP production in cells pretreated with the antagonist bPTH-(3-34)A. Thus, monensin potentiated PTH receptor loss only in cells pretreated with PTH agonists, indicating that antagonist-occupied receptors may be processed differently from agonist-occupied receptors in bone cells. The data further suggest that the attenuation of PTH stimulation of cAMP production in treated bone cells may be, at least in part, due to receptor-mediated endocytosis of the hormone.

In a double-blind controlled study, 15 patients received 1,25-dihydroxycholecalciferol (1,25[OH]2D3) (0.5-1.5 microgram/day) and 16 patients received vitamin D3 (D3) (400-1,200 IU/day). The patients receiving 1,25(OH)2D3 had a rise in mean serum calcium concentration from 9.05 +/- 0.15 to 10.25 +/- 0.20 mg/dl (p less than .001) with a return to 9.37 +/- 0.16 (p less than .001) in the post-control period; however, hypercalcemia (greater than 11.5 mg/dl) occurred in 5 of 15 patients. Likewise, patients who received 1,25(OH)2D3 but not those given D3 had a reversible decrease in immunoreactive parathyroid levels. 9 of 12 patients given D3 had serial iliac crest bipsies showing histologic deterioration, while 6 of 7 patients who received 1,25(OH)2D3 were improved or unchanged (p less than 0.025). Bone mineral and calcium content decreased in patients on D3 (p less than .05) but not in those on 1,25(OH)2D3. We conclude that the administration of 1,25(OH)2D3 to dialysis patients: (1) has a calcemic effect. (2) decreases levels of immunoreactive parathyroid hormone, and (3) is associated with histologic improvement in bone disease.

Preoperative localizing studies are essential for patients with persistent or recurrent hyperparathyroidism requiring reoperation, because of loss of normal tissue planes and because the hyperfunctioning parathyroid tissue that remains is more likely to be situated in an ectopic position. The value of noninvasive and invasive localizing techniques was evaluated in 59 consecutive patients undergoing reoperation for persistent (40 patients) or recurrent (19 patients) hyperparathyroidism. Magnetic resonance imaging was performed in 17 patients; 11 results (65%) were positive, 3 (18%) were negative, and 3 (18%) were false-positive. Ultrasonography was performed in 52 patients; 29 (56%) were positive, 16 (31%) were negative, and 7 (13%) were false-positive. Computed tomography was performed on 41 patients; 19 (46%) were positive, 16 (39%) were negative, and 6 (15%) were false-positive. Thallium chloride 201-technetium 99m pertechnetate scans were used in 39 patients; 19 (49%) were positive, 11 (28%) were negative, and 9 (13%) were false-positive. One or more of these noninvasive tests was positive in 78% of the cases. Highly selective venous catheterization with measurement of immunoreactive parathyroid hormone concentration localized the abnormal parathyroid gland in 20 of 28 patients (71%) overall and in 8 of the 14 patients (57%) whose tumors were not identified by the noninvasive techniques. Since false-positive results were common, a combination of localizing studies was helpful in identifying the abnormal gland. Fifty-three of the 59 patients (90%) were successfully treated at the initial reoperation and three were successfully treated at a second reoperation. Advances in parathyroid localization have contributed to the improved surgical results in patients with persistent or recurrent hyperparathyroidism.

The relative biologic activities of native human parathyroid hormone, hPTH (1-84), native bovine parathyroid hormone, bPTH (1-84), and their respective synthetic, NH2-terminal, biologically-active (1-34) fragments were compared in vitro using adenylate cyclase preparations from human, chicken, and rat renal cortex. The concentrations of the hormones required for half-maximal stimulation of the enzymes were determined from dose response curves. bPTH (1-84) had greater apparent activity than hPTH (1-84), using rat or chicken renal adenylate cyclase, but, with human renal adenylate cyclase, the apparent activities of the two hormones were equal. Synthetic hPTH (1-34) possessed about 1/10 of the apparent activity of hPTH (1-84) in all three adenylate cyclase systems. However, (GLU22)bPTH (1-34) was about equal inapparent activity to bPTH (1-84) in the three systems. We propose that different rates of hormone degradation at or near renal receptor sites may be responsible for the dependence of the relative biologic activity on the assay system used. In the case of hPTH a peptide chain longer than (1-34) may be required for the full biologic activity of the hormone...

The immunoreactive parathyroid hormone (iPTH) in the plasma of hyperparathyroid man consists largely of carboxyl (COOH)-terminal fragments of the hormone. Although these fragments have been thought to arise principally or solely from peripheral metabolism of intact human PTH {hPTH(1-84)} secreted from the parathyroid gland, there is disagreement about the source of iPTH fragments in vivo. To reexamine this question, we fractionated peripheral and thyroid or parathyroid venous effluent sera from four patients with primary hyperparathyroidism using a high-resolution gel filtration system (Bio-Gel P-150 columns run by reverse flow). The column effluents were analyzed using two PTH radioimmunoassays, one directed toward the amino(NH(2))-terminal region of the molecule, the other toward the COOH-terminal region. In all four thyroid or parathyroid venous effluent sera studied, iPTH was 9-180 times higher than in peripheral serum from the same patient; after fractionation, hPTH(1-84) accounted for only a portion of the total iPTH (35-55% with the assay directed toward the COOH-terminal region of hPTH, >90% with the NH(2)-terminal directed assay.) The remaining iPTH eluted from Bio-Gel P-150 after hPTH(1-84) as NH(2)-or COOH-terminal hPTH fragments. These results suggest that parathyroid tumors secrete large quantities of hPTH fragments. Based on estimates of their molar concentrations in serum, tumor-secreted COOH-terminal hPTH fragments could account for most of these peptides in peripheral serum if their survival times were, as estimated by several other workers, 5-10 times that of hPTH(1-84). We conclude that, in contrast to published information, secretory products of hyperfunctioning parathyroid tissue are probably a major source of serum PTH immunoheterogeneity.

We have developed an animal model to study the pathogenesis of secondary hyperparathyroidism by inducing stable uremia in Sprague-Dawley rats by selective microligation of terminal branches of the left renal artery, followed by right nephrectomy. After 4 weeks the animals were killed, the parathyroid glands were removed and weighed, and blood samples were obtained. Of 30 rats, uremia developed in 22 (73%; uremic group) and eight (27%) died or did not become uremic. A sham-operated group of 15 rats served as control (control group). Creatinine levels were 1.8 +/- 0.5 mg/dl in the uremic group versus 0.5 +/- 0.1 mg/dl in the control group (p less than 0.0001). Parathyroid glands were hyperplastic in all rats with uremia and were heavier than parathyroid glands of control animals (70.3 +/- 26 vs 19.1 +/- 8 micrograms; p less than 0.0001). In the group with uremia, parathyroid hormone levels were increased over those of the control group (112.6 +/- 13 vs 28.9 +/- 6.2 pg/ml; p less than 0.0001), whereas osteocalcin levels were similar (36.6 +/- 11 vs 37.5 +/- 1 ng/ml). Serum calcium, phosphate, and alkaline phosphatase levels were similar in both groups. Our model can be used to test hypotheses concerning the treatment of secondary hyperparathyroidism and the relative pathogenetic relevance of vitamin D deficiency and phosphate retention.