Dual-energy x-ray absorptiometry in osteopetrosis

We have used dual-energy x-ray absorptiometry (DXA) in evaluation and follow-up of a patient with osteopetrosis, before and after cord blood transplantation. Other methods of follow-up in such cases have been described, but the use of DXA has not previously been reported. We have shown that DXA offers a safe means of assessing disease progression, the timing of treatment, and response after therapy for osteopetrosis.

Final height of Japanese patients with X-linked hypophosphatemic rickets: effect of vitamin D and phosphate therapy

X-linked hypophosphatemic rickets (XLH) is one of the most common causes of rickets in infancy and childhood. Combination therapy of vitamin D and phosphate is generally used for patients with XLH. Effect of treatment of vitamin D and phosphate during childhood on final height of XLH has to be elucidated in Japanese. There have been only three Caucasian studies on final height of XLH with treatment since childhood. Purpose of this study is to report adult height and therapeutic effect of 22 Japanese participants (5 males, 17 females) with XLH who were treated with phosphate (33-200 mg/kg/day as phosphorus divided into 3 or 4 doses) and vitamin D (vitamin D2 or 1alpha-hydroxyvitamin D3) for more than five years and evaluate effect of the treatment on the final height retrospectively. Final height (FHt) for all participants was -1.69+/-11.11 SD. FHt (-1.69+/-1.11 SD) was significantly higher than height at the initiation of treatment (-2.38+/-0.88 SD) for all participants (P<0.01). In conclusion, combination therapy of vitamin D and phosphate improved final height of Japanese patients with XLH as is similar to previous Caucasian studies.

What is the optimal regimen for vitamin D?

The past 30 years have seen substantial advances in our understanding of the pathogenesis of the mineral, hormonal and skeletal disorders that comprise renal osteodystrophy. The introduction of calcitriol and alfacalcidol as treatments for this disorder in the early 1970s represented an enormous step forward in clinical practice, but unfortunately, the subsequent refinement of these therapies still leaves us well short of the ideal: hyperphosphatemia and hypercalcemia induced by the vitamin D metabolites, and failure to control parathyroid hyperplasia, all remain problematic. Novel pulsed regimens using alfacalcidol and calcitriol, while clearly effective, have not fulfilled initial high expectations of superiority in the context of comparative studies. New vitamin D metabolites, some of which have exhibited desirable selectivity in experimental settings with reduced tendency to raise phosphate and/or calcium while maintaining good control of the parathyroid glands, are now being evaluated. Of these, 22-oxacalcitriol, paricalcitol (19 nor-1,25 dihydroxyvitamin D2) and doxercalciferol (1 alpha-hydroxyvitamin D2) have all shown high efficacy when compared with placebo, but so also did alfacalcidol and calcitriol in similar studies in the 1970s and 1980s. The results of randomized studies comparing the new vitamin D metabolites with current standard therapy (alfacalcidol or calcitriol) are either not yet available or show uncertain benefits in relation to hypercalcemia, hyperphosphatemia and hyperparathyroidism. The impact of these new metabolites on the increasing prevalence of low turnover bone disease is unknown, although experimentally there is evidence of potentially important differences at the level of the skeleton.

Resolution of vitamin D insufficiency in osteopenic patients results in rapid recovery of bone mineral density

Vitamin D insufficiency is characterized biochemically by the presence of secondary hyperparathyroidism, which can contribute to bone loss in osteopenic patients. Over a 2-yr period of evaluation of 118 consecutive, free living patients with osteopenia or osteoporosis, we identified 18 subjects with depressed serum 25-hydroxyvitamin D (250HD; < or = 14 ng/mL). Twelve of these subjects harbored a low 25OHD level and consented to undergo replacement with 50,000 IU vitamin D2 twice weekly for 5 weeks. Five hundred thousand units of oral vitamin D2 resulted in significant increases in 25OHD (+24.3+/-16.9 ng/mL; P < 0.001) and the fasting urinary calcium/creatinine excretion ratio (+0.06+/-0.004; P = 0.01) and significant decreases in the serum concentration of PTH (-32.9+/-36.9 pg/mL; P < 0.001) and osteocalcin (-4.9+/-2.4 ng/mL; P < 0.001). Vitamin D repletion was associated with a significant 4-5% annualized increase in bone mineral density at both the lumbar spine (P < 0.001) and the femoral neck (P = 0.03), indicating that resolution of vitamin D insufficiency in a population of patients with low bone mass results in a rapid rebound increase in bone mineral density.

[Disseminated ischemic necrosis and livedo racemosa in a chronic dialysis patient with calciphylaxis]

Calciphylaxis occurred in a 40-year old female patient with end-stage renal failure. The patient developed livedo racemosa ("livedo reticularis") with painful skin necrosis and ulcers involving multiple areas of the hip and legs after 22 years of hemodialysis. X-ray-examinations revealed calcinosis of peripheral arteries, especially of the pelvis, thigh and hands, while histological examinations showed a fibrosis and calcinosis of small subcutaneous arteries. A generalized cutaneous microangiopathy could be demonstrated by transcutaneous oxygen pressure measurements. Laboratory data showed a moderate secondary hyperparathyroidism with mild elevation of calcium-phosphate product. In addition to the hemodialysis an attempt was made to improve the microcirculation by vasoactive drugs. The clinical course was characterized by slow healing of the ulcers and occurrence of new areas of cutaneous necrosis. Calciphylaxis is a rare late complication in patients with advanced, often end-stage renal failure. It has characteristic histopathological features and is frequently, but not always, associated with a disturbed calcium and phosphorus metabolism and mildly elevated levels of parathyroid hormone. Calciphylaxis is classified as a special type of metastatic calcinosis.

Paricalcitol, a new agent for the management of secondary hyperparathyroidism in patients undergoing chronic renal dialysis

Patients with end-stage renal disease commonly develop secondary hyperparathyroidism. Calcitriol may be administered to such patients to decrease the synthesis and secretion of parathyroid hormone (PTH) and to help maintain calcium and phosphorus homeostasis. However, the doses of calcitriol required to suppress serum PTH concentrations can lead to hypercalcemia or hyperphosphatemia in many patients undergoing hemodialysis. Paricalcitol is a new vitamin D analogue that is safe and effective in suppressing elevated concentrations of PTH in patients with established hyperparathyroidism who are maintained on chronic hemodialysis. As with vitamin D, the biologic action of paricalcitol is mediated through activation of the vitamin D receptor (VDR). The VDR functions as a ligand-induced transcription factor regulating the rate of expression of genes that are involved in controlling not only calcium homeostasis and bone remodeling but also hormone secretion, inhibition of cell growth, and induction of cell differentiation. In vitro studies have shown that paricalcitol inhibits PTH secretion from bovine parathyroid cells in a dose-dependent manner. Studies in renally insufficient rats demonstrated that paricalcitol caused approximately 10 times less elevation of serum calcium concentrations than calcitriol. In clinical studies, paricalcitol effectively decreased PTH by about 60% over a 12-week period. Mean serum concentrations of calcium were significantly increased but remained within the normal range. There were occasional (5/414 determinations) transient elevations in serum calcium above the upper limit of normal in some (5/401) patients. Serum phosphorus values did not change significantly compared with baseline, although they tended to be slightly higher in the paricalcitol-treated group than in the group receiving placebo. Elevations of the calcium-times-phosphorus product were relatively few but occurred more often in the paricalcitol than in the placebo group. The terminal half-life of paricalcitol was 5 to 7 hours in healthy subjects; in patients undergoing hemodialysis, it was 14 hours. Adverse events associated with paricalcitol use included, among others, chills, feeling unwell, fever, sepsis, palpitations, dry mouth, gastrointestinal bleeding, nausea, vomiting, edema, light-headedness, and pneumonia. Paricalcitol should be considered as an alternative to calcitriol in the treatment of patients who are undergoing maintenance hemodialysis for end-stage renal disease, as it has a decreased potential to induce hypercalcemia and hyperphosphatemia. Additional studies are required to determine the long-term effects of therapy.

[Exanthematic pustulosis of pregnancy: favorable evolution using calcium and vitamin D2]

A 26-year-old pregnant woman was hospitalized in an emergency setting for a skin eruption. She had developed pustules distributed on round patch-like areas of rash localized at the umbilicus and the larger skin folds. She was given calcitriol and calcium with good results. Systemic steroids are usually given for exanthematic pustulosis of pregnancy but with variable efficacy. Few cases of successful treatment with calcium and vitamin D have been reported. We suggest this alternative treatment could be useful in other cases.

Therapy of secondary hyperparathyroidism with 19-nor-1alpha,25-dihydroxyvitamin D2

Secondary hyperparathyroidism contributes to significant morbidity in patients with chronic renal failure. The treatment of this disorder with vitamin D compounds, such as calcitriol, although effective at suppressing parathyroid hormone (PTH) secretion, may promote the development of hypercalcemia and hyperphosphatemia, thus increasing the risk for metastatic calcification. A new vitamin D analogue, 19-nor-1alpha,25-(OH)2D2 (paricalcitol; Zemplar, Abbott Laboratories, Inc, Chicago, IL) has recently been developed for the treatment of secondary hyperparathyroidism, and, in experimental animals, it was found to be less calcemic and phosphatemic than calcitriol. In double-blind clinical trials, paricalcitol effectively decreased the levels of PTH by 60%, yet the mean serum calcium values remained within the normal range. The few episodes of hypercalcemia that occurred in the paricalcitol-treated patients (8 of 400 determinations > or =11.0 mg/dL in 7 patients) were associated with marked decreases in PTH levels (87% +/- 2% less than baseline) and absolute values of PTH less than 100 pg/mL in four of the seven patients. PTH values less than 100 pg/mL, however, occurred in 15 patients, but were not invariably associated with frank hypercalcemia, although serum calcium levels increased to 10.63 +/- 0.3 mg/dL, slightly greater than the upper limits of normal. Additional studies to evaluate the conversion from calcitriol to paricalcitol therapy showed that a dose ratio of 1:4 (calcitriol:paricalcitol) could maintain control of high levels of PTH without significant alterations in serum calcium and phosphorus levels. These studies indicate that effective control of hyperparathyroidism can be achieved with paricalcitol therapy with minimal perturbation of serum calcium and phosphorus levels, and may have a therapeutic advantage over current treatment strategies.

Effects of 19-nor-1,25(OH)2D2, a new analogue of calcitriol, on secondary hyperparathyroidism in uremic rats

The active metabolite of vitamin D, calcitriol [1,25(OH)2D3] suppresses parathyroid hormone (PTH) gene transcription and PTH secretion. Although 1,25(OH)2D3 is effective in suppressing secondary hyperparathyroidism in uremic patients, the mandatory use of large amounts of calcium salts to control serum phosphorus may preclude in some patients the use of ideal therapeutic doses of 1,25(OH)2D3 because of hypercalcemia. We have studied a new analogue of calcitriol,19-nor-1,25(OH)2D2 that possesses low calcemic and phosphatemic activity. We have clearly demonstrated that this analogue of calcitriol can suppress secondary hyperparathyroidism without inducing hypercalcemia or hyperphosphatemia in uremic rats. In addition, this analogue of vitamin D supresses pre-pro PTH messenger RNA in a similar fashion to that of 1,25(OH)2D3. Contrary to the effect of 1,25(OH)2D3 that increases the intestinal vitamin D receptor, this analogue of vitamin D suppresses the intestinal vitamin D receptor. This finding may be critical for the lack of calcemic activity of 19-nor-1,25(OH)2D2 seen in these studies. One of the explanations for the lack of an increasing intestinal VDR is the fact that 19-nor-1,25(OH)2D2 decreases endogenous levels of 1,25(OH)2D3. In summary, we have shown that 19-nor-1,25(OH)2D2, a new analogue of calcitriol is effective in suppressing PTH in uremic rats with secondary hyperparathyroidism. In addition, there is a significant decrease in the VDR in the intestine, which may explain in part the less calcemic and hyperphosphatemic effect of this analogue.

Suppression of parathyroid hormone secretion in hemodialysis patients by a novel vitamin D analogue: 19-nor-1,25-dihydroxyvitamin D2

In this double-blind, placebo-controlled, randomized, multicenter study, 35 patients with end-stage renal disease undergoing maintenance hemodialysis were treated three times weekly for 4 weeks with either 19-nor-1,25-dihydroxyvitamin D2 (paricalcitol) intravenously at doses ranging from 0.04 to 0.24 microg/kg or placebo. Eligible patients with secondary hyperparathyroidism (HPT; intact parathyroid hormone [iPTH] level > 300 pg/mL) were initially withdrawn from any existing vitamin D therapy over a 4-week washout period and then randomized to treatment for 4 weeks with either paricalcitol or placebo. Overall, there was a clinically and statistically significant reduction in iPTH level for patients receiving paricalcitol compared with placebo (P = 0.006). The study end point for efficacy was at least a 30% reduction from maximum baseline in iPTH level for 75% of the patients receiving paricalcitol per dosing group. The study end point for efficacy was at least a 30% reduction from maximum baseline in iPTH for 75% of patients receiving paricalcitol per dosing group. Sixty-eight percent (15 of 22) of patients receiving paricalcitol attained this efficacy end point regardless of dosage received (0.04, 0.08, 0.16, and 0.24 microg/kg). Eighty-three percent (5 of 6) of the patients in each of the paricalcitol groups receiving 0.16- and 0.24-microg/kg dosages attained the efficacy end point. Only two patients receiving placebo attained the iPTH end point. There were no clinically relevant differences in serum calcium (Ca) or phosphorus (P) levels between the group treated with paricalcitol and that treated with placebo. Although there was a statistically significant difference between the change from baseline to final-visit Ca levels in the paricalcitol group and the placebo group (P < 0.001), the final-visit mean Ca level in the paricalcitol group was within the normal range (9.44 mg/dL). There was no statistically significant difference between groups for the change from baseline in P level (P = 0.625). Only one patient treated with paricalcitol developed hypercalcemia before or coincident with the iPTH end point. Three other patients receiving paricalcitol experienced elevated serum Ca levels subsequent to reaching the iPTH end point, with iPTH reductions of 83% to 98%. There were no significant differences between patients treated with paricalcitol and patients treated with placebo in adverse reactions. These results show that paricalcitol safely and effectively reduces iPTH levels in hemodialysis patients with secondary HPT.

Fluoride and bone: a second look. No use in osteoporosis

(1) Data on fluoride efficacy in secondary prevention of osteoporotic fractures were contradictory when we last examined the file, in 1990. We now re-examine the clinical file on fluoride with more follow-up and new clinical trial data. (2) In 354 postmenopausal women with a history of vertebral fracture (secondary prevention), a comparative trial (the FAVOS trial) showed that moderate-dose fluoride for 2 years did not reduce the incidence of new vertebral fractures relative to calcium plus vitamin D. Furthermore, fluoride caused more cases of lower-limb pain. (3) In 110 postmenopausal women with a history of vertebral fracture, a trial showed that fluoride (sustained-release form) + calcium was more effective than calcium alone in preventing vertebral fractures. (4) No pertinent trial on fluoride in primary prevention has been published since 1991.

19-Nor-1-alpha-25-dihydroxyvitamin D2 (Paricalcitol) safely and effectively reduces the levels of intact parathyroid hormone in patients on hemodialysis

Paricalcitol (19-nor-1alpha-25-dihydroxyvitamin D2), a new vitamin D analog developed for the treatment of secondary hyperparathyroidism, was evaluated in three double-blind, placebo-controlled, dose-escalating, randomized multicenter trials. A total of 78 patients (40 Paricalcitol injection, 38 placebo) achieved treatment phase eligibility, which included intact parathyroid hormone (iPTH) > or = 400 pg/ml, normalized serum calcium levels between 8.0 and 10.0 mg/dl, and calcium x phosphorus product values less than 75. Study end points included a decrease in iPTH of at least 30% or a maximum of five dose escalations. After a 4-wk washout, paricalcitol or placebo was administered intravenously three times per week after dialysis for 12 wk. Study drug was started at a dose of 0.04 microg/kg and was increased by 0.04 microg/kg every 2 wk to a maximal allowable dose of 0.24 microg/kg or until at least a 30% decrease in serum iPTH was achieved. The dose of paricalcitol that decreased iPTH by at least 30% became the maintenance dose. Of 40 patients receiving paricalcitol, 27 (68%) had at least a 30% decrease in serum iPTH for 4 consecutive weeks, compared with three of 38 patients (8%) receiving placebo (P < 0.001). For patients who received 12 wk of treatment with paricalcitol, the levels of iPTH decreased significantly from 795+/-86 to 406+/-106 pg/ml (P < 0.001), whereas the values for PTH were 679+/-41 pg/ml before and 592+/-41 pg/ml after 12 wk of therapy in patients receiving placebo (P=NS). Also, there was a significant difference between treatment groups for the change from baseline PTH levels (P < 0.001). Paricalcitol treatment resulted in a significant reduction in serum alkaline phosphatase from 148+/-23 U/L to 101+/-14 U/L (P < 0.001) in patients treated for 12 wk compared with 120+/-9 U/L to 130+/-11 U/L (P=NS) in patients receiving placebo for 12 wk. Importantly, hypercalcemia did not occur before achieving target serum iPTH levels in any of the paricalcitol-treated patients. There was no significant difference for the change from baseline in serum phosphorus within or between treatment groups. There was no significant difference in adverse events between the paricalcitol and placebo-treated groups. These studies demonstrate that paricalcitol safely and effectively suppresses iPTH levels in hemodialysis patients. This second generation vitamin D analog may have a wider therapeutic window than current vitamin D preparations, and thus may allow reduction in PTH with less hypercalcemia.

Vitamin D replacement in Asians with diabetes may increase insulin resistance

We report three cases of vitamin D replacement in British Asians with vitamin D deficiency and non-insulin-dependent diabetes mellitus. In all cases, replacement resulted in an increase in insulin resistance and a deterioration of glycaemic control.

Unique 24-hydroxylated metabolites represent a significant pathway of metabolism of vitamin D2 in humans: 24-hydroxyvitamin D2 and 1,24-dihydroxyvitamin D2 detectable in human serum

We have produced evidence for a new metabolic pathway for vitamin D2 in humans involving the production of 24-hydroxyvitamin D2 (24OHD2) and 1,24-dihydroxyvitamin D2 [1,24-(OH)2D2]. These metabolites were produced after either a single large dose (10(6) IU) of vitamin D2 or repeated daily doses between 10(3) and 5 x 10(4) IU. We developed assay systems for the metabolites in human serum and showed that in some chronically treated patients, the concentration of 1,24-(OH)2D2 equalled that of 1,25-(OH)2D2 at about 100 pmol/L. The metabolites were identified by high performance liquid chromatography with diode array spectrophotometry for 24OHD2 and by high resolution gas chromatography-mass spectrometry for 1,24-(OH)2D2. We show that 1,24-(OH)2D2 synthesis can be stimulated by PTH, indicating a renal origin for this metabolite and postulate that it is formed from 24OHD2, which may be synthesized in liver. We conclude from this study that vitamin D2 gives rise to two biologically active products, 1,24-(OH)2D2 and 1,25-(OH)2D2, and that 1,24-(OH)2D2 could be an attractive naturally occurring analog of 1,25-(OH)2D3 for clinical use.

Fluoride salts are no better at preventing new vertebral fractures than calcium-vitamin D in postmenopausal osteoporosis: the FAVOStudy

Although fluoride salts have been shown to be capable of linearly increasing spinal bone mineral density (BMD) in postmenopausal osteoporosis, the effects of this gain in density on the vertebral fracture rate remain controversial. We conducted a 2-year multicenter, prospective, randomized, double-masked clinical trial in 354 osteoporotic women with vertebral fractures (mean age 65.7 years). They received either fluoride (208 patients), given as sodium fluoride (50 mg/day) or as monofluorophosphate (200 mg/day or 150 mg/day), or a placebo (146 patients). All patients received daily supplements of 1 g of calcium (Ca) and 800 IU of vitamin D2 (D). A 1-year open follow-up on Ca-D was obtained in 124 patients. After 2 years the fluoride group and the Ca-D group had increased their lumbar BMD by 10.8% and 2.4% respectively (p = 0.0001). However, the rate of patients with at least one new vertebral fracture, defined by semiquantitative assessment and evaluable on an intention-to-treat basis in 89% of patients, was similar in the fluoride groups and the Ca-D group. No difference between the three fluoride regimens was found. The percentage of patients with nonvertebral fractures was not different in the fluoride and Ca-D groups (1.9% and 1.4% respectively for hip fractures). A lower limb pain syndrome occurred more frequently in the fluoride groups. In the 124 patients followed for 1 year after cessation of fluoride therapy, the percentage of patients with at least one new vertebral fracture after 36 months was identical to the percentages in the previous fluoride group and the Ca-D group. We conclude that fluoride-Ca-D regimen was no more effective that Ca-D supplements for the prevention of new vertebral fractures in women with postmenopausal osteoporosis.

X-linked hypophosphatemia: normal renal function despite medullary nephrocalcinosis 25 years after transient vitamin D2-induced renal azotemia

Nephrocalcinosis (NC) detected by ultrasound is a recognized abnormality for some patients with X-linked hypophosphatemia (XLH) who received vitamin D2 and inorganic phosphate therapy, but is commonly observed in XLH patients treated with 1,25-dihydroxyvitamin D3 and inorganic phosphate supplementation. Nevertheless, long-term follow-up of kidney function in XLH patients with NC detected ultrasonographically has not been reported. We investigated two women with XLH, ages 31 (patient 1) and 39 (patient 2) years, each of whom had suffered at least one documented episode of vitamin D2-induced hypercalcemia and renal azotemia during childhood. Patient 2 had also been treated with inorganic phosphate. No medications for XLH had been taken during adulthood. Renal ultrasonography at our institution demonstrated marked bilateral medullary NC in both women. No other explanation was found for their NC that apparently occurred several decades earlier from medical therapy for XLH. Detailed studies (including creatinine clearance, beta2-microglobulin excretion, and fasting urinary osmolality and acidification) revealed no impairment of kidney function in either patient. Our findings indicate that subradiographic medullary NC acquired during medical therapy for XLH may persist for decades, but with no adverse renal sequelae. Definitive (long-term) assessment of kidney function in the XLH population with NC, however, will be necessary to fully understand the risk of current medical treatment for this most common heritable form of rickets.

Use of erythropoietin, active vitamin D3 metabolites, and alkali agents in predialysis patients

Studies in rats with renal ablation indicate that anemia lessens, whereas its vigorous correction with recombinant human erythropoietin (r-HuEPO) worsens systemic and glomerular hypertension, factors known to promote progression of chronic renal failure (CRF). However, in human studies, use of r-HuEPO in predialysis patients has not been associated with worsening renal function, provided blood pressure control is achieved. Histological evidence of bone disease is common in early renal failure, and deficits in calcitriol synthesis seem to be an important factor in the pathogenesis of secondary hyperparathyroidism (HPTH) in early CRF. Reports to data, on the use of low dose active vitamin D metabolites in predialysis patients, indicate either a reversible decline or no decline in renal function. Adynamic bone disease, however, may ensure during such therapy if excessive reductions in serum intact parathyroid hormone concentrations occur. Recent data suggest that chronic metabolic acidosis decreases albumin synthesis, increases muscle proteolysis, and induces negative nitrogen balance in patients with CRF. Despite these experimental data, the clinical relevance of correction of metabolic acidosis in end-stage renal disease (ESRD) is still not defined. Even though therapy of metabolic acidosis in the adult patient with CRF remains conjectural at this time, reports indicate that its correction might lead to healing of osteomalacia and osteopenia, and possibly may decrease protein degradation and improve growth in children with CRF.

Saccharated ferric oxide (SFO)-induced osteomalacia: in vitro inhibition by SFO of bone formation and 1,25-dihydroxy-vitamin D production in renal tubules

A 60-year-old man with portal hypertensive gastropathy due to type C liver cirrhosis developed severe bone pains, marked hypophosphatemia with inappropriately increased urinary excretion of phosphate (%TRP; 9.6%), and hyperalkaline phosphatasia, after intravenous administration of saccharated ferric oxide (SFO) at a dose of 80-240 mg/week over a period of more than 5 years. The total iron infused was estimated to be more than 25 g. On a diagnosis of SFO-induced osteomalacia, the infusion of iron was immediately discontinued, and phosphate and vitamin D2 (1000 IU/day) were administered. Serum levels of 25-OHD2 increased after 1 week, whereas levels of 1,25-(OH)2D2 did not increase until 3 months later, accompanied by improvement of renal tubular reabsorption of phosphate and gradual improvement of the bone pains. The patient has been doing well for the last 2 years, with normal serum levels of phosphate, calcium, and alkaline phosphatase, without any supplementation of phosphate, vitamin D, or iron-containing agents. In primary culture of neonatal mouse renal tubules, in which 1,25-(OH)2D3 was produced from 25-OHD3 in response to PTH, SFO significantly inhibited PTH-induced production of 1,25-(OH)2D3 at 30 mumol/L, which is attainable in the urine of patients receiving a therapeutic intravenous dose of SFO. Furthermore, SFO decreased the calcium content and inhibited 45Ca incorporation in cultured fetal mouse parietal bones at 3 mumol/L. Such SFO concentration may be transiently observed in the plasma of patients receiving excessive intravenous doses of SFO for a prolonged period. These in vitro findings together with the clinical observations suggest that SFO, after filtration through the glomerulus and reabsorption in the proximal renal tubules, impaired proximal renal tubular function, such as tubular reabsorption of phosphate and 1 alpha-hydroxylase activity, leading to hypophosphatemic osteomalacia. Furthermore, it is highly likely that SFO in the peripheral blood, when transferrin is saturated with iron, may impair bone formation and aggravate osteomalacia. Although SFO-induced osteomalacia is reversible simply by discontinuation of the agent, excessive and prolonged administration of SFO should be avoided.

Simplified method for the determination of 25-hydroxy and 1alpha,25-dihydroxy metabolites of vitamins D2 and D3 in human plasma. Application to nutritional studies

A simplified method for the determination of 25-hydroxy and 1alpha,25-dihydroxy metabolites of vitamins D2 and D3 in human plasma was developed. Plasma samples were deproteinizated and applied to a Bond Elut C18OH cartridge to separate 25-hydroxyvitamin D (25-OH-D) and 1alpha,25-dihydroxyvitamin D [1,25(OH)2D] fractions. The 25-OH-D fraction was purified by a Bond Elut C18 cartridge and 25-OH-D2 and 25-OH-D3 were assayed by HPLC using a Zorbax SIL column. The 1,25(OH)2D fraction obtained above was subsequently applied to HPLC using a Zorbax SIL column to separate 1,25(OH)2D2 and 1,25(OH)2D3 fractions which were determined by a radioreceptor assay (RRA) using calf thymus receptor. The method was applied to nutritional studies.

Subclinical vitamin D deficiency in neonates: definition and response to vitamin D supplements

To determine the biological criteria for neonatal vitamin D deficiency, serum 25-hydroxyvitamin D (calcidiol), parathyroid hormone (PTH), calcium, phosphates, and alkaline phosphatase (ALP) activity were measured during the winter-spring period in 80 healthy neonates and their mothers 3-6 d after delivery. A longitudinal 3-mo survey of the serum biology of 52 of these neonates consuming formula was also performed to test the influence of their neonatal vitamin D status on the effects of two oral ergocalciferol supplements (500 and 1000 IU or 12.5 and 25 micrograms/d). At birth, 63.7% of the infants had calcidiol concentrations < or = 30 nmol/L. Most of them had no other biological sign evocative of vitamin D deficiency, but 14 neonates had low calcidiol concentrations and serum PTH concentrations > 60 ng/L, the upper limit of the adult normal range. They also had a significantly lower mean serum calcium concentration than did neonates with calcidiol concentrations > 30 nmol/L. On the basis of the association of low calcidiol concentrations (< or = 30 nmol/L) and high PTH concentrations (> 60 ng/L) as criteria for vitamin D deficiency, 24% of the neonates born to unsupplemented mothers were found to be vitamin D-deficient. Neonatal vitamin D status influenced the response of the infants to vitamin D supplements. Neonates with no sign of vitamin D deficiency showed similar changes in their serum calcidiol, calcium, phosphate, and PTH concentrations and ALP activity and no toxic effect (hypercalcemia or highly elevated calcidiol concentration) was observed whatever their vitamin D intake. In contrast, neonates with subclinical vitamin D deficiency had normalized serum PTH within 1 mo only when they were given 1000 IU ergocalciferol (25 micrograms)/d in addition to their formula.

Recovery from metabolic bone disease in a girl with vitamin D deficiency rickets associated with primary hyperparathyroidism

We describe a 13 year-old Ethiopian girl with vitamin D deficiency rickets. Hypercalcemia, increased serum alkaline phosphatase and PTH levels, together with low serum levels of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D suggested the co-existence of primary hyperparathyroidism. The surgical removal of a parathyroid adenoma led to bone healing and normalization of blood chemistry. We conclude that vitamin D deficiency masked the hyperparathyroidism and hypercalcemia, while excess PTH secretion delayed the cure of rickets until successful parathyroidectomy had been carried out.