Novel homozygous variant in BMP1 associated with a rare osteogenesis imperfecta phenotype

Osteogenesis imperfecta (OI) is characterized by bone fragility and increased fracture susceptibility. BMP1 variants have been reported in the rare OI type XIII, specifically referred to herein as BMP1-associated autosomal recessive (AR) OI. We report the clinical presentation and diagnostic evaluation of a patient found to have a novel homozygous variant in BMP1. We also provide an overview of reported BMP1 variants to date, with discussion focusing on the use of bisphosphonate therapy in these patients. A 7-year-old male with speech and motor delay sustained five bilateral tibial fractures with minimal trauma since age 2.5 years. At age 6, he developed severe back pain after a fall. Diffuse spinal osteopenia and multiple vertebral compression fractures (VCF) at T9, L1, L3, and L5 were identified. Total hip BMD was generous (adjusted Z-score* = 1.76), and femoral neck BMD was high (adjusted Z-score* = 2.67). VCFs precluded assessment of lumbar spine BMD. Genetic analysis identified a homozygous missense variant in exon 4 of BMP1 (c.C505T; p.Arg169Cys). Unlike most forms of OI, patients with BMP1-associated AR OI may have normal or paradoxically increased BMD, making BMD and fracture risk correlation difficult. While bisphosphonates (BP) may help reduce recurrent fractures and provide symptomatic relief, the broad phenotypic spectrum and underlying bone pathology, often in the setting of increased BMD, complicate management. HR-pQCT assessment of bone microarchitecture and quality may aid in the decision of BP therapy and subsequent monitoring. Evidence is limited with respect to the effectiveness of BP in this rare form of OI. *Z-score was adjusted for height Z-score.

A founder mutation in the TCIRG1 gene causes osteopetrosis in the Ashkenazi Jewish population

Osteopetrosis is a rare and heterogeneous genetic disorder characterized by dense bone mass that is a consequence of defective osteoclast function and/or development. Autosomal recessive osteopetrosis (ARO) is the most severe form and is often fatal within the first years of life; early hematopoietic stem cell transplant (HSCT) remains the only curative treatment for ARO. The majority of the ARO-causing mutations are located in the TCIRG1 gene. We report here the identification and characterization of an A to T transversion in the fourth base of the intron 2 donor splice site (c.117+4A→T) in TCIRG1, a mutation not previously seen in the Ashkenazi Jewish (AJ) population. Analysis of a random sample of individuals of AJ descent revealed a carrier frequency of approximately 1 in 350. Genotyping of five loci adjacent to the c.117+4A→T-containing TCIRG1 allele revealed that the presence of this mutation in the AJ population is due to a single founder. The identification of this mutation will enable population carrier testing and will facilitate the identification and treatment of individuals homozygous for this mutation.

Ectopic cardiac calcification associated with hyperparathyroidism in a boy with hypophosphatemic rickets

An adolescent with hypophosphatemic rickets developed cardiac calcifications in the absence of hypercalcemia or elevation of the phosphocalcic product (the product of the total serum calcium and phosphorus concentrations). Cardiac calcifications led to aortic and mitral valve dysfunction, myocardial calcification, and arrhythmia. Hyperparathyroidism probably played a significant role in the development of this complication, which emphasizes the necessity for intermittent assessment of parathyroid status in individuals receiving medical therapy for hypophosphatemic rickets.

Mutational analysis and genotype-phenotype correlation of the PHEX gene in X-linked hypophosphatemic rickets

PHEX is the gene defective in X-linked hypophosphatemic rickets. In this study, analysis of PHEX revealed mutations in 22 hypophosphatemic rickets patients, including 16 of 28 patients in whom all 22 PHEX exons were studied. In 13 patients, in whom no PHEX mutation had been previously detected in 17 exons, the remaining 5 PHEX exons were analyzed and mutations found in 6 patients. Twenty different mutations were identified, including 16 mutations predicted to truncate PHEX and 4 missense mutations. Phenotype analysis was performed on 31 hypophosphatemic rickets patients with PHEX mutations, including the 22 patients identified in this study, 9 patients previously identified, and affected family members. No correlation was found between the severity of disease and the type or location of the mutation. However, among patients with a family history of hypophosphatemic rickets, there was a trend toward more severe skeletal disease in patients with truncating mutations. Family members in more recent generations had a milder phenotype. Postpubertal males had a more severe dental phenotype. In conclusion, although identifying mutations in PHEX may have limited prognostic value, genetic testing may be useful for the early identification and treatment of affected individuals. Furthermore, this study suggests that other genes and environmental factors affect the severity of hypophosphatemic rickets.

Vitamin D-deficiency rickets in adopted children from the former Soviet Union: an uncommon problem with unusual clinical and biochemical features

Rickets is an unusual disorder in international adoptees. Three international adoptees from the former Soviet Union recently presented with rickets. Their clinical and laboratory presentations were atypical, reflecting circumstances unique to children adopted from orphanages in the former Soviet Union and the early initiation of vitamin D therapy. In these children, radiographs of the long bones were diagnostic when the classically diagnostic biochemical parameters, calcium and 25OHD(3) levels, were normal.

Phosphaturic mesenchymal tumor-induced rickets

We describe two prepubertal girls with oncogenic rickets. The first patient, 9 years of age, presented with recent-onset lower-extremity pain. The second girl, presented at 4 years of age following a 9-month period of muscle weakness, bone pain, and poor linear growth. Laboratory analyses in both patients revealed hypophosphatemia and hyperphosphaturia; elevated circulating alkaline phosphatase activity was present in one of them. Radiographic evidence of a generalized rachitic process was evident in both cases. Computerized tomography of the paranasal sinuses and facial bones in patient 1 revealed a small lesion eroding through the inner table of the left mandibular ramus. Microscopic examination of this mass revealed a spindle cell neoplasm with chondroid material, dystrophic calcification, and both osteoclast-like and fibroblast-like cells. Prominent vascularity and marked atypia were present. These features are consistent with a phosphaturic mesenchymal tumor of the mixed connective tissue variant. In the second patient, computerized tomography revealed a lytic lesion located in the right proximal tibia, with histologic features consistent with a phosphaturic mesenchymal tumor of the nonossifying fibroma-like variant. Resection of each tumor resulted in rapid correction of the phosphaturia and healing of the rachitic abnormalities. A careful search for small or occult tumors should be carried out in cases of acquired phosphaturic rickets.

Hyperthyroidism: a novel feature of the tubulointerstitial nephritis and uveitis syndrome

Tubulointerstitial nephritis and uveitis syndrome presents with either renal or ocular manifestations, and associated weight loss. We report two adolescents with transient hyperthyroidism early in the course of the syndrome. Hyperthyroidism may represent an unrecognized feature of the disorder and potentially contributes to the accompanying weight loss. Thyroid function should be evaluated in patients with tubulointerstitial nephritis and uveitis syndrome and symptomatic therapy provided when necessary.

Early puberty in Williams syndrome

Pubertal development was evaluated in nine males and 16 females with Williams syndrome (WS). Our results indicate that puberty in WS occurred earlier than in published population controls; specifically, 90% of menstruating females reached menarche and 83% of pubertal males showed Tanner III pubic hair development prior to the age of 12 years. The sequence of pubertal development was normal, bone age was always consistent with, or in excess of, chronological age, and there was evidence of central (hypothalamic-pituitary mediated) activation as the cause of early puberty in a subset of subjects.

Changes in bone turnover in young women consuming different levels of dietary protein

Although high protein diets are known to increase urinary calcium excretion and induce negative calcium balance, the impact of dietary protein on bone turnover and fractures is controversial. We therefore evaluated the effect of dietary protein on markers of bone turnover in 16 healthy young women. The experiment consisted of 2 weeks of a well balanced diet containing moderate amounts of calcium, sodium, and protein followed by 4 days of an experimental diet containing one of three levels of protein (low, medium, or high). On day 4, serum and urinary calcium, serum PTH, 1,25-dihydroxyvitamin D, serum osteocalcin, bone-specific alkaline phosphatase, and urinary N-telopeptide excretion were measured. Urinary calcium excretion was significantly higher on the high than on the low protein diet. Secondary hyperparathyroidism occurred on the low protein diet. Urinary N-telopeptide excretion was significantly greater during the high protein than during the low protein intake (48.2 +/- 7.2 vs. 32.7 +/- 5.3 nM bone collagen equivalents/mM creatinine; P < 0.05). There was no increase in osteocalcin or bone-specific alkaline phosphatase when comparing the low to the high diet, suggesting that bone resorption was increased without a compensatory increase in bone formation. Our data suggest that at high levels of dietary protein, at least a portion of the increase in urinary calcium reflects increased bone resorption.

Osteocalcin production in primary osteoblast cultures derived from normal and Hyp mice

Rickets and osteomalacia are characteristic features of the Hyp mouse model of human X-linked hypophosphatemia. Hyp mice demonstrate elevated circulating osteocalcin levels, as well as altered regulation of osteocalcin by 1,25(OH)2D3. Whether this osteocalcin abnormality is intrinsic to the osteoblast, or mediated by the in vivo milieu, has not been established. We therefore characterized osteocalcin production and its regulation by 1,25(OH)2D3 in primary cultures of murine osteoblasts and examined osteocalcin and its messenger RNA in response to 1,25(OH)2D3 in cultures of Hyp mouse-derived osteoblasts. Cell viability and osteocalcin production are optimal when murine cells are harvested within 36 h of age. Murine primary osteoblast cultures mineralize and produce osteocalcin in a maturation-dependent fashion (as demonstrated in other species), and continuous exposure to 1,25(OH)2D3, beginning at day 9 of culture, inhibits osteoblast differentiation and osteocalcin production and prevents mineralization of the culture. However, in contrast to other species, exposure to 1,25(OH)2D3, added later (days 17-25) in culture, does not stimulate osteocalcin but arrests osteocalcin production at current levels. Ambient media levels of osteocalcin were no different in cultures from Hyp mice and their normal litter mates, and the down-regulatory response to 1,25(OH)2D3 was comparable in cultures from normal and Hyp mice. Furthermore, expression of osteocalcin messenger RNA in murine cultures is reduced with exposure to 1,25(OH)2D3, and there is no difference between normal and Hyp cultures in this response. Thus, primary murine osteoblasts manifest a species-specific effect of 1,25(OH)2D3 on osteocalcin production. Furthermore, the increased serum osteocalcin production seen in intact Hyp mice, and the altered response to 1,25(OH)2D3 in Hyp mice, are not observed in osteoblast cultures derived from the mutant strain. These data indicate that abnormalities of osteocalcin described in intact Hyp mice require factors other than those present in cultured cells.

Increased circulating concentrations of parathyroid hormone in healthy, young women consuming a protein-restricted diet

Increasing dietary protein induces hypercalciuria and a negative calcium balance. Despite this, the influence of dietary protein on the parathyroid hormone (PTH) I-a-hydroxylase axis is not well understood. We therefore examined the effect of three amounts of dietary protein: low (0.7 g/kg), medium (1.0 g/kg), and high (2.1 g/kg) on mineral metabolism and the PTH-1-alpha-hydroxylase axis in 16 healthy women aged 26.7 +/- 1.3 y. By day 4, urinary calcium decreased significantly with the low-protein diet and increased significantly with the high-protein diet compared with the medium-protein diet (control). Also by day 4, there were striking elevations in serum PTH and calcitriol [1,25-dihydroxyvitamin D] in subjects consuming the low-protein diet. Serum PTH, by two different assays, was 1.5-2.4 times higher and by day 14 1.6-2.7 times higher during the low-protein diet compared with the medium-protein diet. This was accompanied by a significant increase in both nephrogenous cyclic adenosine monophosphate (cAMP), a sensitive and specific indicator of PTH bioactivity, and serum calcitriol by day 14. In comparison, there were relatively minor changes in the calcitropic hormones with the medium- and high-protein diets. The stimulus for the elevation in PTH induced by protein restriction is unclear, but probably does not involve a simple renal mechanism and could reflect either a decline in intestinal calcium absorption, a reduction of bone turn-over, or both. Our data indicate that dietary protein is a powerful regulator of calcium metabolism. Further study is needed to both clarify the mechanisms by which these changes are induced and to better define the amount of dietary protein that will optimize skeletal health in young women.

Cardiovascular abnormalities in patients with X-linked hypophosphatemia

Treatment for X-linked hypophosphatemia (XLH; vitamin D metabolites and phosphate salts) may result in hypercalcemia, hypercalciuria, nephrocalcinosis, and hyperparathyroidism. Cardiovascular abnormalities occur in association with these complications, but have not been reported in XLH. We hypothesized that such abnormalities may occur in XLH and evaluated cardiovascular status in 13 patients with this disease. All patients were asymptomatic and had normal cardiovascular physical examinations and Holter studies. Serum calcium and creatinine clearance were normal in all. However, all patients had mild to moderate nephrocalcinosis. Left ventricular hypertrophy was diagnosed by electrocardiogram in three and by ultrasonography in seven children. Baseline blood pressure (BP) was normal (mean +/- SD, 116 +/- 15/74 +/- 6 mm Hg). During exercise stress testing, systolic BP increased in all patients, but the maximal systolic pressure was less than that in healthy age- and sex-matched controls (156 +/- 20 vs. 175 +/- 23; P = 0.002, by t test). An abnormal increase in diastolic BP occurred at all levels of work load in XLH patients; their peak exercise diastolic BP was 91 +/- 12 vs. 72 +/- 6 mm Hg in controls (P < 0.0001, by t test). Whether these abnormal findings are primary defects in XLH or represent complications of treatment is unclear. Patients with XLH should be monitored closely for the development of hypertension and left ventricular hypertrophy. Investigation of the mechanisms involved and establishment of therapeutic guidelines are indicated.

Sonography of congenital adrenal hyperplasia due to partial deficiency of 3beta-hydroxysteroid dehydrogenase: a case report

We report the case of a patient with congenital adrenal hyperplasia (CAH) secondary to a partial deficiency of 3beta-hydroxysteroid dehydrogenase. This form occurs in less than 1 % of all patients with CAH. Sonographic evaluation of the adrenal glands demonstrated width and length measurements significantly above normal values. The sonographic findings are not diagnostic of the particular enzyme deficiency in CAH, and the exact etiology should be pursued with laboratory investigation.

New perspectives on the biology and treatment of X-linked hypophosphatemic rickets

This article updates the practicing pediatrician's knowledge of the hypophophatemic disorders that may occur in children. The classic X-linked disorder is emphasized. Details of clinical manifestations, the wide spectrum of disease severity, and complications of the disorder in adults are reviewed. Recent research, new genetic findings, and speculations regarding pathophysiology are discussed. A strategy for approaching medical treatment of X-linked hypophosphatemic rickets is provided, together with complications of treatment and treatment after cessation of growth.

Osteocalcin abnormalities in Hyp mice reflect altered genetic expression and are not due to altered clearance, affinity for mineral, or ambient phosphorus levels

The Hyp mouse manifests rickets and renal wasting of phosphorus. We previously reported elevated circulating osteocalcin in Hyp mice, and a paradoxical decrease in response to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. To investigate these abnormalities further, we characterized in detail the response of circulating osteocalcin to 1,25-(OH)2D3 and compared skeletal osteocalcin in normal and Hyp mice. The affinity of osteocalcin for hydroxyapatite and the protein's clearance were compared in Hyp and normal animals. Finally, the response of osteocalcin messenger RNA (mRNA) to 1,25-(OH)2D3 was examined in normal mice, Hyp mice, and normal mice subjected to dietary phosphorus deprivation. Multiple (n = 3-6) daily doses of 1,25-(OH)2D3 are required to increase serum osteocalcin levels in normal C57 BL/6 mice; the effect is apparent by 6 h and persists for at least 24 h after injection. Single doses of up to 50 ng have no significant effect. In contrast, an approximately 50% decrement in circulating osteocalcin occurs after a single dose of 1,25-(OH)2D3 in Hyp mice. Osteocalcin clearance in Hyp mice appears to be normal. Bone osteocalcin per U calcium or phosphorus is normal in Hyp mice, suggesting that its affinity for hydroxyapatite is normal. Osteocalcin mRNA from Hyp mice is expressed in greater abundance than that from normal animals, reflecting the differences in circulating levels of the protein. Similarly, osteocalcin mRNA from Hyp mice decreases in response to 1,25-(OH)2D3, whereas an increase in osteocalcin message is seen in normal animals. These studies indicate that normal mice are relatively resistant to 1,25-(OH)2D3 stimulation of osteocalcin production. Furthermore, the differences between Hyp and normal mice in circulating osteocalcin reflect differences in the regulation of gene expression.

24,25 Dihydroxyvitamin D supplementation corrects hyperparathyroidism and improves skeletal abnormalities in X-linked hypophosphatemic rickets--a clinical research center study

Therapy for X-linked hypophosphatemia (XLH) only partially corrects skeletal lesions and is often complicated by hyperparathyroidism. 24,25(OH)2 D3 improves skeletal lesions in a murine model of XLH and suppresses PTH secretion in animals. Therefore, we undertook a placebo-controlled trial of 24,25(OH)2 D3 supplementation to standard treatment in patients with XLH to improve bone disease and reduce hyperparathyroid complications. Fifteen subjects with XLH receiving standard treatment [1,25(OH)2 D3 or dihydrotachysterol plus phosphate] were evaluated, supplemented with placebo, and reevaluated one yr later. 24,25(OH)2 D3 supplementation was then begun and studies repeated after another year. Each patient underwent a detailed evaluation of calcium homeostasis over a 24-h period. Rachitic abnormalities were assessed radiographically in children. Adults underwent bone biopsies. 24,25(OH)2 D3 normalized PTH values in nine subjects (peak PTH was 46.5 +/- 6.6 pmol/L at entry, 42.3 +/- 5.9 pmol/L after placebo, and 23.3 +/- 5.4 pmol/L after 24,25(OH)2 D3). Nephrogenous cAMP decreased at night, coincident with the decrease in PTH, and serum phosphorus was slightly greater with 24,25(OH)2 D3. Radiographic features of rickets improved during 24,25(OH)2 D3 supplementation in children, and osteoid surface decreased in adults. 24,25(OH)2 D3 is a useful adjunct to standard therapy in XLH by effecting correction of hyperparathyroidism and improvement of rickets and osteomalacia.

Media calcium attenuates mitochondrial 1,25(OH)2D production in phosphorus or vitamin D-deprived rats

Although PTH and hypophosphatemia are the best known stimulators of 25-hydroxyvitamin D-1 alpha-hydroxylase, 1,25(OH)2D3 production in rats and humans can be modulated by circulating calcium, independent of PTH. To test whether calcium modulates this function directly in mitochondria, we examined effects of calcium on 1 alpha-hydroxylase in isolated mitochondrial preparations under basal and stimulated conditions. Rats were fed a low phosphorus (or matched control) diet for 4 or 7 d or a vitamin D-deficient (or matched control) diet for 2, 4, or 7 wk. Renal mitochondria were isolated and assayed for 1 alpha-hydroxylase activity in the presence or absence of added calcium. Calcium did not alter 1 alpha-hydroxylase in rats on control diets. After 4 d of low phosphorus diet, 1 alpha-hydroxylase was increased 2-fold over basal activity; media calcium prevented this stimulatory response. By 7 d the calcium effect was not evident. After 4 wk of vitamin D deprivation, activity was approximately 30-fold greater than controls; calcium reduced this response significantly (15-fold). A significant, but less marked inhibition of activity by calcium was present in rats subjected to 7 wk of vitamin D deprivation. Extramitochondrial calcium can directly modulate 1,25(OH)2D3 production, but this effect appears to be secondary to the primary physiologic regulators of this function. The calcium effect can be overcome after longer term exposure to phosphorus deprivation, but is sustained in the presence of long term vitamin D deprivation.

Secretion of a large molecular-weight form of insulin-like growth factor by a primary renal tumor

A 5-year-old boy with an abdominal mass was found to have a primary renal tumor of poorly identifiable histology. Prior to resection of the tumor, the patient exhibited several episodes of biochemical hypoglycemia. The hypoglycemia did not recur after operation. Analysis of tumor tissue and of pre- and post-operative sera by column chromatography showed elevated insulin-like growth factor II (IGF-II) levels in the tumor; an abnormal large-molecular weight precursor form of IGF-II (pro-IGF-II) comprised 53% of total IGF-II in the tumor and 42% in preoperative serum. No pro-IGF-II was found in the serum 6 weeks post-operatively. Abnormal IGF-II secreted by the tumor may have mediated the hypoglycemia seen prior to tumor resection. This pediatric renal tumor is the first to our knowledge for which an association of non-islet cell tumor-related hypoglycemia and elevated tumor IGF-II content has been described.

Safety of parenteral hydroxypropyl beta-cyclodextrin

Post-treatment data were collected on a patient who received intravenous hydroxypropyl beta-cyclodextrin in a dose of 1.5 g/kg in 1985. Although no untoward effects were observed in this patient, rarely occurring agitation and pulmonary edema have been noted after injections into rabbits and dogs, respectively. These complications are analyzed here on the basis of symptoms and on the effects of hydroxypropyl beta-cyclodextrin on the biochemistry of a representative lipid, cholesterol, which were studied in rats. It is hypothesized that these untoward effects of parenteral hydroxypropyl beta-cyclodextrin are due to complex formation, with lipid mediators of pathological responses, of which prostaglandins are one example. These mediators normally have brief and localized functions; if hydroxypropyl beta-cyclodextrin happens to be injected when these mediator systems are activated, their influence and the responses of the organism may be increased.

Nocturnal hyperparathyroidism: a frequent feature of X-linked hypophosphatemia

Parathyroid function is described as normal in patients with phosphopenic rickets before initiation of therapy with phosphate salts; however, hyperparathyroidism is an occasional complication of treatment. We observed a higher than expected frequency of hyperparathyroidism in patients with phosphate-wasting rickets, present before treatment in some patients and, more frequently, after the onset of treatment. To better define parathyroid status in hypophosphatemic rickets, we sampled 12 affected children and 7 affected adults every 4 h for 1 day and measured PTH in assays detecting midmolecule fragments (cPTH) and intact hormone (iPTH). All children and 4 adults were receiving a vitamin D preparation and phosphate salts; 3 adults were untreated. Mean cPTH, iPTH, and nephrogenous cAMP excretions in each group of patients were greater than in controls. Exaggerated nocturnal rises in both cPTH and iPTH characterized the profile in patients. Seventeen patients demonstrated frankly elevated cPTH at night, with peak values at midnight, whereas no control individual did. Although mean iPTH values in patients increased at night, they did not exceed the upper limit of normal. Hyperparathyroidism in hypophosphatemic rickets occurs in both children and adults, may be present in untreated patients, is predominantly nocturnal, and is characterized by exaggerated secretion of midmolecule fragments. This manifestation of hypophosphatemic rickets is more widespread than currently recognized; we speculate that it may contribute to the pathogenesis of nephrocalcinosis and precede the development of tertiary hyperparathyroidism.

Thyrotropin-secreting adenoma in an adolescent girl without increased serum thyrotropin-alpha

A 13-year-old girl with poor weight gain and pubertal delay was referred for hyperthyroidism. Slightly elevated levels of circulating thyroid hormones failed to suppress circulating thyrotropin (TSH) levels. Despite appropriate thyrotropin-releasing hormone stimulation of TSH secretion, a thyrotropin-secreting pituitary adenoma was identified as the cause of inappropriate TSH secretion.

Osteocalcin and its message: relationship to bone histology in magnesium-deprived rats

These studies examine effects of brief Mg deprivation on bone histomorphometry and on secretion and synthesis of the specific osteoblast product, osteocalcin. Osteocalcin mRNA was determined in calvaria-derived cells and was correlated to circulating concentrations of the protein after 8 days of Mg deprivation. Circulating osteocalcin was decreased in Mg-deprived rats when compared with pair-fed normal rats after 8 days of Mg deprivation, with no significant changes in calcium or 1,25-dihydroxyvitamin D [1,25(OH)2D]. Serial sampling demonstrated a difference in osteocalcin levels by 2 days of Mg deprivation, before any changes in circulating calcium or parathyroid hormone were present. Although circulating osteocalcin is decreased in Mg-deprived animals, levels can be stimulated with 1,25(OH)2D3. Osteocalcin mRNA is reduced after Mg deprivation, suggesting that low circulating levels are due, at least in part, to reduced osteocalcin synthesis. Mg-deprived rats had diminished bone volume and abnormal histological features consistent with disorganized and chaotic bone remodeling. These findings indicate that low-Mg intake during growth can alter the quality and quantity of bone and suggest that Mg deprivation may contribute to the development of osteoporosis.

Hydroxypropylcyclodextrins in parenteral use. II: Effects on transport and disposition of lipids in rabbit and humans

Hydroxypropyl ethers of cyclodextrins, after parenteral administration, come into contact with lipids in tissues and in circulation and form water-soluble inclusion complexes with these lipids. A single intravenous administration of hydroxypropyl-beta-cyclodextrin to a hereditary hyperlipidemic Watanabe rabbit slightly and temporarily decreased the level of total cholesterol in serum. Single injections of hydroxypropyl-alpha-cyclodextrin and of the corresponding gamma-homologue, both of which are less potent solubilizers of cholesterol, had lesser effects. Repeated administration of hydroxypropyl-beta-cyclodextrin to rabbits led to a gradual increase in total cholesterol in circulation and eventually to a slight relief of atherosclerotic lesions in the thoracic aorta. The only untoward effects of repeated treatments (total doses of up to 40 g/kg) were vacuoles in cells of proximal convoluted tubules in the kidneys. Repeated administration also strongly increased cholesterol in urine, probably because of excretion of the soluble cholesterol-hydroxypropyl-beta-cyclodextrin complex. Proteins in urine increased significantly, whereas triglycerides increased only moderately after repeated administrations. Intravenous infusion of hydroxypropyl-beta-cyclodextrin into a patient with hypervitaminosis A led to a release of liver-stored retinoids into serum in quantities much higher than those that could be directly solubilized by hydroxypropyl-beta-cyclodextrin. Levels of total cholesterol in the circulation of this patient decreased during the infusion. Thus, hydroxypropylcyclodextrins may serve as artificial lipid carriers in the circulation, and because the exchanges that involve inclusion complexation occur very quickly, the presence of hydroxypropylcyclodextrins in organisms may catalytically augment the establishment of equilibria in lipid distribution.

Dissociation of phosphaturia and 25(OH)D-1 alpha-hydroxylase trophism using a novel analogue of parathyroid hormone

Certain parathyroid hormone (PTH) analogues have been shown to selectively impair some but not all physiological actions of PTH. In this study, transaminated rat (r) PTH [TA-rPTH-(1-34)], a PTH analogue that differs from the rPTH-(1-34) fragment in that the NH2-terminal alanine is converted to pyruvate, was infused into mice to determine its properties in vivo and specifically to determine whether stimulation of 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase) activity was more dependent on concomitant renal handling of phosphate or on generation of adenosine 3',5'-cyclic monophosphate (cAMP). High-performance liquid chromatography-purified TA-rPTH-(1-34) was infused into C57BL mice at 10 or 30 pmol/h for 24 h. At 30 pmol/h, TA-rPTH-(1-34) was comparable with rPTH-(1-34) in its hypophosphatemic and phosphaturic effects but was less potent than rPTH-(1-34) in raising serum calcium. TA-rPTH-(1-34) was markedly less effective in stimulating renal 1 alpha-hydroxylase than rPTH-(1-34). Stimulation of urinary cAMP excretion occurred after infusion with TA-rPTH-(1-34), but this effect was significantly less than that seen with rPTH-(1-34). These findings indicate that PTH-induced hypophosphatemia and phosphaturia can be uncoupled from PTH stimulation of 1 alpha-hydroxylase. Furthermore, cAMP-related signal transduction appears to be more significant in regulation of 1 alpha-hydroxylase than mechanisms that mediate PTH-sensitive phosphate transport, independent of cAMP.

Development and validation of a radioimmunoassay for mouse osteocalcin: paradoxical response in the Hyp mouse

The hypophosphatemic (Hyp) mouse is a model for human familial hypophosphatemic rickets. To test the hypothesis that there is an osteoblastic defect in these animals, serum osteocalcin levels were measured in Hyp mice and their normal littermates. Furthermore, the effects of phosphorus deprivation, phosphorus loading, and 1,25-dihydroxyvitamin D3 administration on serum osteocalcin levels were examined. Osteocalcin was purified from mouse hindlimbs, and a polyclonal antibody to this material was produced in a goat. The antibody recognized native and decarboxylated mouse osteocalcin, but could not recognize osteocalcin from several other species. A RIA was developed which had a minimal detection limit of 0.4 nmol/liter (2.2 micrograms/liter) and half-maximal displacement at 2.7-3.3 nmol/liter (14.8-18.2 micrograms/liter). The intraassay coefficient of variation was 6.4%, while the interassay coefficient of variation was 12%. Dilutions of mouse serum samples varied by less than 15%. Analytical recovery was typically greater than 90%. Serum osteocalcin concentrations in Hyp and normal mice were shown to decrease with age. However, circulating osteocalcin levels in Hyp mice were higher than those in their normal littermates regardless of the age of the animal (P less than 0.001). One week of a high phosphorus diet resulted in an increase in serum phosphate in normal and Hyp mice, but serum osteocalcin concentrations were unaffected. On the other hand, dietary phosphorus deprivation for 4 weeks resulted in comparable hypophosphatemia in both Hyp and normal mice, and serum osteocalcin increased in both groups of animals. Intraperitoneal injection of 30 ng/day 1,25-dihydroxyvitamin D3 for 7 days resulted in a 215 +/- 33% increase in serum osteocalcin in normal animals, while the same regimen produced a 250 +/- 29% decrease in the Hyp mouse. Our results are consistent with the hypothesis that abnormal osteoblastic activity is present in Hyp mice. Furthermore, hypophosphatemia may be a general regulator of osteocalcin synthesis or secretion in the mouse.

Effect of growth hormone treatment on hyperinsulinemia associated with Turner syndrome

To determine whether the insulin resistance in patients with Turner syndrome, which may be exaggerated by treatment with human growth hormone, leads to excessive insulin secretion, we applied the hyperglycemic glucose-clamp technique to produce a standard hyperglycemic stimulus (6.9 mmol/L, or 125 mg/dl, greater than fasting plasma glucose level for 120 minutes) in seven patients with Turner syndrome and in seven healthy children. These studies were repeated in the patients after 6 to 12 months of therapy with growth hormone. Fasting plasma levels of insulin were comparable in control subjects and patients before therapy but increased significantly in the patients after 6 to 12 months of treatment with growth hormone. Despite identical glucose increments in the two groups during the glucose-clamp procedure, both first- and second-phase insulin responses were significantly greater in the patients than in the control subjects. Moreover, the hyperinsulinemic responses to glucose were markedly exaggerated in the patients after their treatment with growth hormone, reaching values (first phase 474 +/- 100 pmol and second phase 826 +/- 100 pmol; p less than 0.02 vs pretreatment values) that were almost threefold greater than those in control subjects (p less than 0.001). Nevertheless, the rate of insulin-stimulated glucose metabolism during the last 60 minutes of the clamp procedure was similar in all three groups of studies. Glycosylated hemoglobin, total cholesterol level, and blood pressure remained normal in patients after therapy with growth hormone. We conclude that glucose-stimulated insulin response is increased in patients with Turner syndrome and that these alterations are further exaggerated by treatment with growth hormone. These hyperinsulinemic responses appear to compensate for reductions in insulin sensitivity.

Insulin resistance: an early metabolic defect of Turner's syndrome

To evaluate whether insulin resistance contributes to the increased risk of diabetes in patients with Turner's syndrome, we measured insulin sensitivity (using the euglycemic insulin clamp technique, 40 mU/m2.min) and whole body glucose and lipid oxidation (assessed by indirect calorimetry) in two groups of nondiabetic patients with Turner's syndrome and age-matched normal controls. Group 1 consisted of eight young patients (mean age, 10 +/- 0.8 yr) who had never received hormone therapy, and group 2 consisted of five patients (mean age, 17.6 +/- 1.4 yr) who had been or were on estrogen therapy. In group 2, [3-3H]glucose was also infused during the euglycemic clamp to assess hepatic sensitivity to insulin. During the euglycemic clamp, insulin-stimulated glucose metabolism was decreased in both groups of patients [group 1, 8.4 +/- 1.0 vs. 14.7 +/- 2 mM/m2.min in controls (P less than 0.05); group 2, 9 +/- 0.7 vs. 11.7 +/- 0.9 mM/m2.min in controls (P less than 0.05)]. The impairment of insulin-stimulated glucose metabolism in patients with Turner's syndrome was accounted for by reduced nonoxidative glucose disposal; glucose oxidation rose to a similar extent in Turner patients and normal controls. Insulin-induced suppression of hepatic glucose production (group 2) and plasma FFA and branched chain amino acid levels in Turner patients was also indistinguishable from that in normal controls. Our data suggest that in patients with Turner's syndrome, insulin resistance is a very early metabolic defect that may be restricted to nonoxidative pathways of intracellular glucose metabolism.

Renal 25-hydroxyvitamin D-1 alpha-hydroxylase activity and mitochondrial phosphate transport in Hyp mice

The Hyp mouse is a homologue of the X chromosome-linked human disease, familial hypophosphatemic rickets (FHR). In FHR, reduced renal tubular brush-border membrane transport of phosphate results in hypophosphatemia and rickets. Both humans with FHR and Hyp mice have abnormal regulation of 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase), a mitochondrial enzyme found in proximal renal tubular cell epithelia, the apparent site of defective brush-border membrane phosphate transport. No common pathophysiology for these defects has been demonstrated. We hypothesized that phosphate transport may be present in renal mitochondria from Hyp mice and that its regulation may be deranged in parallel with the mitochondrial 1 alpha-hydroxylase. Using inhibitor-stop techniques described for measurement of phosphate transport in liver mitochondria, we examined mitochondria in normal and Hyp mouse kidney and found them to be comparable. We performed manipulations known to alter 1 alpha-hydroxylase differentially in normal and Hyp mice, i.e., phosphorus deprivation and phosphorus loading, and found no effect on mitochondrial phosphate transport. We also subjected Hyp and normal mice to calcium and vitamin D deprivation; this maneuver resulted in no significant changes in mitochondrial phosphate transport in Hyp or normal mice but confirmed the earlier observation that 1 alpha-hydroxylase activity is stimulated to a greater degree in normal mice than Hyp mice after this diet. Furthermore, administration of 1,25-hydroxyvitamin D3 depresses 1 alpha-hydroxylase activity in mitochondria from both normal and Hyp mice but has no effect on mitochondrial phosphate transport. We conclude that the mechanism of abnormal vitamin D metabolism in Hyp mice is not related to a primary defect in renal mitochondrial phosphate transport.

Variable expression of 5 alpha-reductase deficiency: presentation with male phenotype in a child of Greek origin

A male infant with perineal hypospadias and a small phallus bound in chordee is described. Biochemical investigation at age 9 months after hCG stimulation revealed a testosterone to dihydrotestosterone (DHT) ratio of 40, a markedly elevated value suggestive of deficient steroid 5 alpha-reductase activity. The diagnosis of 5 alpha-reductase deficiency was confirmed by elevated urinary 5 beta/5 alpha-steroid metabolite ratios and demonstration of defective 5 alpha-reductase activity in cultured fibroblasts from the patient's scrotum and foreskin. Application of DHT cream to the patient's abdomen raised circulating levels of DHT to the adult male range. Two courses of DHT given nightly for 3 and 4 months resulted in phallic enlargement. Surgical release of the chordee and hypospadias repair have resulted in normal male appearance of the genitalia. This case illustrates the heterogeneity of the 5 alpha-reductase deficiency phenotype.

Effect of parathyroid hormone-like peptides on 25-hydroxyvitamin D-1 alpha-hydroxylase activity in rodents

The role of vitamin D metabolism in the humoral hypercalcemia of malignancy syndrome (HHM) is unclear. We studied in vivo and in vitro effects of synthetic parathyroid hormone-like peptides (PTH-LPs) on rodent renal 25-OHD-1 alpha-hydroxylase activity. Infusion of mice with PTH-LP-(1-36) at 10 pmol/h for 12 and 24 h showed significant (429 +/- 139% and 937 +/- 413%, respectively) stimulation of control enzyme activity. Infusion for 36 h demonstrated diminution of activity to levels nearer to the unstimulated state (228 +/- 36% of control). In that maximal activity was observed after 24 h of infusion, we examined 1 alpha-hydroxylase activity after variable dosages of PTH-LP-(1-36) at this time point. Animals infused with PTH-LP-(1-36) at dosages of 2.5, 10, and 30 pmol/h for 24 h demonstrated 1 alpha-hydroxylase activities of 0.71 +/- 0.12, 4.74 +/- 2.09, and 9.91 +/- 1.01 ng.mg protein-1.20 min-1 (means +/- SD), respectively, all significantly greater than control activity (0.51 +/- 0.20 ng.mg protein-1.20 min-1). PTH-LP-(1-36) and PTH-LP-(1-74) were comparable in potency to bovine (b)PTH-(1-34) in stimulating 1 alpha-hydroxylase. Direct in vitro incubation of PTH-LP-(1-36) with renal slices resulted in stimulation of 1 alpha-hydroxylase activity up to 200% of control levels, comparable to that seen with equimolar concentrations of bPTH-(1-34).(ABSTRACT TRUNCATED AT 250 WORDS)

Vitamin D metabolism in chronic childhood hypoparathyroidism: evidence for a direct regulatory effect of calcium

We noted the presence of elevated levels of circulating 1,25-dihydroxyvitamin D (83 pg/ml (200 pmol/L), with low total serum calcium concentration (6.5 mg/dl (1.88 mmol/L), in an untreated adolescent boy with hypoparathyroidism. Furthermore, an inverse relationship between total serum calcium and circulating 1,25-dihydroxyvitamin D levels was evident during treatment with 1,25-dihydroxyvitamin D3. We examined this relationship with a 33-hour intravenous infusion of calcium gluconate in the absence of exogenous 1,25-dihydroxyvitamin D3 therapy. The infusion was accompanied by a gradual increase of both total serum calcium and blood ionized calcium concentrations from hypocalcemic to normocalcemic ranges, and produced a 50% reduction in circulating 1,25-dihydroxyvitamin D values, with minimal changes in circulating phosphorus, magnesium, and 25-hydroxyvitamin D values. These results suggest that calcium-dependent, parathyroid hormone-independent regulation of 1,25-dihydroxyvitamin D production may exist in human beings.

Disturbances of vitamin D metabolism and action during clinical and experimental magnesium deficiency

It has been known since the 1920s that magnesium is influential in calcium homeostasis. In the 1970s it was documented that parathyroid secretion and activity may be impaired in magnesium deficiency. In the past two decades a variety of studies have indicated alterations in circulating vitamin D metabolites in humans, although these observations are not entirely consistent. Animal studies have not consistently demonstrated impaired vitamin D metabolism during relatively brief periods of magnesium deprivation, despite in vitro magnesium dependence of 1 alpha-hydroxylase activity. Studies of the administration of active vitamin D metabolites to humans and animals suggest that skeletal resistance to these compounds in magnesium deficiency may, in part, explain their reduced calcaemic effect during magnesium deficiency.

Metabolism of 25-hydroxyvitamin D in copper-laden rat: a model of Wilson's disease

Wilson's disease results in excess tissue accumulation of copper and is often complicated by skeletal and mineral abnormalities. We investigated vitamin D metabolism in rats fed a copper-laden diet rendering hepatic copper content comparable with that found in Wilson's disease. Injection of 25-hydroxyvitamin D3 [25(OH)D3] resulted in reduced 1,25-dihydroxyvitamin D [1,25(OH)2D] levels in copper-intoxicated rats. In vitro 25(OH)D-1 alpha-hydroxylase activity was impaired in renal mitochondria from copper-intoxicated animals. Activity was also inhibited in mitochondria from controls when copper was added to incubation media. Impaired conversion of 25(OH)D to 1,25(OH)2D occurs in copper intoxication and suggests that altered vitamin D metabolism is a potential factor in the development of bone and mineral abnormalities in Wilson's disease.

Severe hypervitaminosis A in siblings: evidence of variable tolerance to retinol intake

A 2-year-old boy had signs and symptoms of chronic hypervitaminosis A. A course of increasing severity led to eventual death. A younger brother later had similar clinical features. Chicken liver spread containing up to 420 IU/g vitamin A was the likely source of intoxication. Markedly elevated circulating retinyl ester levels have persisted in the surviving sibling for 3 subsequent years despite severe restriction of vitamin A intake. A therapeutic trial of the carbohydrate-derived complexing agent 2-hydroxypropyl-beta-cyclodextrin was initiated. Circulating retinyl esters transiently increased during the infusion (from 407 to 4791 micrograms/dL), and urinary total vitamin A excretion, undetectable before infusion, increased to 23 micrograms/dL after infusion. The frequency of hypervitaminotic episodes has decreased somewhat in the 2 years since the infusion, probably related to dietary vitamin A restriction. The occurrence of this syndrome in two brothers, while a sister ingesting the same diet remains completely healthy, suggests an inherited variance in tolerance to vitamin A intake.

Effect of magnesium depletion on metabolism of 25-hydroxyvitamin D in rats

Resistance to vitamin D in magnesium depletion has been observed in humans and in animal studies. Variable levels of 1,25-dihydroxyvitamin D [1,25(OH)2D] have been reported in patients with magnesium depletion, and studies of vitamin D metabolism in states of magnesium depletion have not yielded consistent results. We examined effects of magnesium deprivation on circulating 1,25(OH)2D levels before and after a loading dose of 25-hydroxyvitamin D3 [25(OH)D3], on in vivo conversion of small doses of radiolabeled 25(OH)D3 to 1,25(OH)2D3 in intact rats, and on in vitro 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase) activity in rat renal mitochondria. The effects of magnesium-free media on mitochondrial 1 alpha-hydroxylase activity was examined. Magnesium depletion did not affect in vivo conversion of 25(OH)D to 1,25(OH)2D. In vitro 1 alpha-hydroxylase activity was comparable in magnesium-replete and -deplete animals and was evident in the absence of added magnesium in incubation media. Our in vivo and in vitro studies are consistent with one another and demonstrate that in the rat conversion of 25(OH)D to 1,25(OH)2D is unimpaired in magnesium deficiency. Resistance to vitamin D in magnesium depletion is likely due to the impaired skeletal responsivity to 1,25(OH)2D, as demonstrated in earlier studies.

Bone fragility, craniosynostosis, ocular proptosis, hydrocephalus, and distinctive facial features: a newly recognized type of osteogenesis imperfecta

We report two infants with bone deformities and multiple fractures reminiscent of osteogenesis imperfecta, but also having ocular proptosis with orbital craniosynostosis, hydrocephalus, and distinctive facial features. Both infants were normal at birth, but multiple compression fractures of the long bones were noted shortly thereafter, followed by extensive demineralization and culminating in recurrent diaphyseal fractures of the weight-bearing bones before the first birthday. The striking similarity of both the distinctive dysmorphic features and the unique pattern of fractures in two unrelated individuals suggests that this is a previously unrecognized form of osteogenesis imperfecta. Despite the craniosynostosis and hydrocephalus, intellectual performance is unimpaired in both individuals. Bone biopsy in one patient revealed decreased bone volume and increased bone resorption without compensatory new bone formation. Extensive laboratory investigations have not identified a cause, nor have they clarified pathogenesis; further elucidation will require the identification and study of new cases.

Progressive tubulointerstitial renal disease in infancy with associated hepatic abnormalities

Clinical, pathologic, and biochemical data are reported in two male infants who had rapidly progressive renal failure, enlarged kidneys, hepatosplenomegaly, and fat malabsorption. One infant, studied prior to the onset of significant renal insufficiency, manifested renal Fanconi syndrome, hyperparathyroidism, and marked hypocalcemia. After a brief period of dialysis, both received renal transplants. Neither has clinical evidence of reoccurrence of the renal disorder in the transplant, but both still have hepatic abnormalities. Morphologic features present in both patients include a renal lesion characterized by tubulointerstitial injury with a tubulocystic component and hepatic abnormalities with bile duct proliferation, portal fibrosis, and inflammation. These cases do not readily conform to any single published diagnostic category, including nephronophthisis-congenital hepatic fibrosis or infantile polycystic kidney disease, and appear to be unique.

Serum osteocalcin concentrations in children with metabolic bone disease

We surveyed both normal children and patient populations to identify the effects of metabolic bone disease and impaired renal function on serum levels of osteocalcin, a vitamin K-dependent protein synthesized in bone. Cord blood osteocalcin was nearly double that of maternal osteocalcin, but there was no correlation between the two. Infants with Apgar scores less than or equal to 7 had a lower mean serum osteocalcin value (8.7 ng/ml, n = 8) than did those with scores of 8 to 10 (16.6 ng/ml, n = 38). Serum osteocalcin elevation coincided with the pubertal growth spurt. In boys, levels decreased to adult values by 18 years of age, as do other indices of bone metabolism; in girls, the levels decreased earlier and had a less pronounced maximum. In children with renal failure, osteocalcin was substantially increased, presumably because of diminished renal clearance of the protein. Children receiving peritoneal dialysis, however, had mean serum concentrations less than half of those seen in children receiving hemodialysis (117 vs 328 ng/ml). The peritoneal dialysate contained significant amounts of osteocalcin, but none was detectable in hemodialysate. Correlation between bone disease and serum osteocalcin was evident in a longitudinal study of one patient with renal failure. Children with various forms of rickets had elevated osteocalcin levels; hypoparathyroidism and osteoporosis were accompanied by variable changes. Serum osteocalcin holds promise as a useful marker of subacute changes in bone metabolism.

Hypoparathyroidism in Wilson's disease

An 11-year-old girl with Wilson's disease presented with mild hypocalcemia (8.0 mg per deciliter), hypophosphatemia (2.7 mg per deciliter), hypercalciuria (569 mg per day), and hyperphosphaturia (tubular reabsorption of phosphate, 67 per cent). The hyperphosphaturia and hypercalciuria were attributed to the Fanconi syndrome, a known component of Wilson's disease. Circulating immunoreactive parathyroid hormone was usually undetectable or, occasionally, detectable at minimal levels in the presence of depressed blood levels of ionized calcium. Normal levels of ionized calcium were not maintained throughout a 24-hour monitoring period. The patient had tetany during a period of rapid reduction in ionized calcium levels, and an appropriate rise in circulating immunoreactive parathyroid levels was never demonstrated. Induced hypocalcemia during citrate infusion did not stimulate parathyroid secretion, nor did infusion of magnesium. We conclude that parathyroid insufficiency may be associated with Wilson's disease. We speculate that it is due to deposition of copper in the parathyroid glands.

Basic pediatrics: a new American physician in an African village hospital

This communication presents a picture of medical practice, with an emphasis on pediatrics, in a rural hospital in the Transkei Republic of Southern Africa. The manner in which this setting appeared to and confronted a new graduate and his attempts to practice medicine are reported. An evaluation of the experience in terms of an education and suggestions for interested students and physicians are described.