Norman H. Bell

Low circulating vitamin D in obesity

SummaryPrevious studies demonstrated decreases in serum 25-hydroxyvitamin D in obese subjects. Studies were carried out to determine whether serum vitamin D is low in obesity. The results indicate that serum vitamin D is significantly lower in obese than in nonobese individuals and may contribute to lower serum 25-hydroxyvitamin D in obesity.

Significant Differential Effects of Alendronate, Estrogen, or Combination Therapy on the Rate of Bone Loss after Discontinuation of Treatment of Postmenopausal Osteoporosis: A Randomized, Double-Blind, Placebo-Controlled Trial

Context Alendronate and conjugated estrogen therapy both increase bone mineral density in postmenopausal women, but is the rate of bone loss greater when alendronate or estrogen therapy is discontinued? Contribution The discontinuation phase of this double-blind, placebo-controlled trial showed loss of spine and trochanter bone mass in postmenopausal women 1 year after withdrawal of estrogen and no such loss after withdrawal of either alendronate or combination therapy with alendronate and estrogen therapy. Cautions The study was not large or long enough to show whether discontinuation of estrogen therapy is associated with more fractures than discontinuation of either alendronate or combination therapy. The Editors Several antiresorptive agents have been shown to increase bone mass and reduce osteoporotic fractures (1-3). Because greater improvements in bone mass in women using therapy are associated with greater reductions in fracture (4, 5), investigators have begun to examine combinations of antiresorptive therapies to achieve more substantial gains in bone mass. Lindsay and colleagues demonstrated that addition of alendronate to hormone replacement therapy in postmenopausal women resulted in greater increases in bone mass than did maintenance of estrogen therapy alone (6). We previously showed that administration of alendronate and estrogen for 2 years in postmenopausal women with low bone mass resulted in statistically significantly greater increases in bone mass at the lumbar spine and femoral neck than those seen in women taking either agent alone (7). Furthermore, combination therapy was safe and resulted in normal findings on histologic examination of bone. In clinical practice, a key concern is the potential for accelerated bone loss when antiresorptive therapy is discontinued. Approximately one third of women discontinue hormone replacement therapy within 1 year of initiation (8). Older studies have demonstrated significant losses in bone mass after discontinuation of hormone replacement therapy (9-11). In contrast, when therapy with oral alendronate, 10 mg/d, is discontinued after osteoporosis treatment, bone mass at the hip and spine are maintained for 1 year (12). However, no head-to-head comparison of hormone replacement therapy and alendronate or the combination of antiresorptive therapy after discontinuation has been done. In addition, future losses in bone mass when patients discontinue therapy must be considered in management of osteoporosis in postmenopausal women. We therefore sought to examine the rate of bone loss after discontinuation of 2 years of alendronate therapy, hormone replacement therapy, or combination therapy. A subset of participants continued to take combination therapy for a third year to determine whether prolonged therapy remained beneficial. Methods Study Participants Four hundred twenty-five postmenopausal women 42 to 82 years of age who had low bone mass were enrolled in a 2-year randomized, double-blind, placebo-controlled clinical trial conducted at 18 centers in the United States (7). Participants were recruited from clinics, private practices, newspaper advertisements, and targeted mailings. All participants who completed the initial study were asked to enroll in the 1-year extension. Participants were told that if they were taking active treatment, they might be randomly allocated to receive placebo or treatment for the third year and that if they were taking placebo, they would continue to do so. Entry criteria for the initial study are described elsewhere (7). All women had had hysterectomy and had a bone mineral density at the lumbar spine that was less than or equal to a T score of 2.0 SDs below the peak bone mass in young adults. Data on presence or absence of ovaries were not collected. Exclusion criteria were metabolic bone disease, a low serum 25-hydroxyvitamin D level, use of medications known to affect bone turnover, renal insufficiency, severe cardiac disease, and recent major upper gastrointestinal disease. The institutional review board at each clinical site approved the extension protocol. After signing the extension consent form and undergoing baseline evaluation for the extension, participants were allocated to blinded treatment on the basis of their original treatment in the first 2 years of the study. The randomization process was centrally determined by a statistician; as in the initial study, treatment allocation was concealed. Design As described for the initial study at each center, patients were randomly allocated to one of four treatment groups: placebo (n = 50); alendronate, 10 mg/d (n = 92); conjugated estrogen, 0.625 mg/d (n = 143); or alendronate, 10 mg/d, plus conjugated estrogen, 0.625 mg/d (n = 140) (Figure 1). The conjugated estrogen used was Premarin (Wyeth-Ayerst, Philadelphia, Pennsylvania). All women received calcium carbonate to provide 500 mg of elemental calcium daily. Figure 1. Design of original 2-year study and reallocation to extension phase for year 3. At the end of the second year, 244 of the 425 women (57%) continued in a 1-year extension of the study (Figure 1). Of these women, 28 who previously received placebo continued to do so. Women who were taking combination therapy were reallocated to continue taking combination therapy (n = 44) or switch to placebo (n = 41). In addition, 50 participants taking alendronate alone and 81 participants taking conjugated estrogen alone for the first 2 years were assigned to placebo for the third year. All patients and investigators remained blinded to medication allocation. Patients continued to receive calcium supplementation during the third year. Outcome Measures Women were examined at month 24 (baseline of the 1-year extension), month 30, and month 36. Bone mineral density of the lumbar spine, hip (femoral neck, trochanter, total hip), and total body were assessed by using dual-energy x-ray absorptiometry with QDR-1000W, QDR-1500, or QDR-2000 series bone densitometers (Hologic, Inc., Bedford, Massachusetts). A standard phantom was used for cross-calibration at all sites. Serum and urine samples were also obtained at months 24, 30, and 36 for assessment of biochemical markers of bone turnover, namely bone-specific alkaline phosphatase and urinary N-telopeptide cross-links of collagen type I, corrected for creatinine. Statistical Analysis We used SAS software, version 6.12, TSLevel 0060, PROCedureGLM (SAS Institute, Inc., Cary, North Carolina) to analyze the data. The primary efficacy end point was the mean difference between groups in the percentage change in bone mineral density at the lumbar spine from month 24 to month 36. Secondary efficacy end points were the mean percentage changes in bone mineral density of the hip and total body and biochemical markers of bone turnover. Overall percentage changes from month 0 to 36 in spine, hip, and total-body bone mineral density were also analyzed. The prespecified analysis was based on an intention-to-treat approach. At study design, we prespecified that all patients who had a baseline measurement and at least one measurement during treatment would be included in the analysis according to the group to which they were randomly allocated. The missing data were approximated by carrying forward the last available value on treatment forward to the missing time point. No data from the original 2-year study were carried forward to the extension period for any assessment of change. Women who violated the protocol were excluded from analysis of biochemical markers, as previously reported (7). Between-group comparisons of bone mineral density and biochemical measures were made by using analysis of variance techniques, with treatment, center, and treatment-by-center as factors. The assumption of homoscedasticity for the analysis of variance model was assessed by using the Levene test, and the normality assumption was assessed by using the ShapiroWilk test (13). If the assumptions were violated, a nonparametric method was used to corroborate the parametric results. The Fisher exact test was used to compare treatment groups for the proportion of participants who exceeded predefined limits of change in laboratory safety variables (13). Power calculations based on estimated sample sizes of 56 and 84 participants in the alendronate/placebo and estrogen/placebo treatment groups, respectively, yielded an estimate of 92% power to detect a 1.5% difference between mean percentage changes from month 24 to month 36 in bone mineral density at the lumbar spine ( = 0.05, two-tailed test). As requested by the journal editors, data on bone mineral density were also analyzed by using a mixed-model analysis, and results of this analysis are presented. An appropriate curvilinear function was fitted to the actual data, and the function was estimated by using all data available across time points for each participant. A model that regressed bone mineral density versus log (month + 1) provided the appropriate fit for the 3-year data and was used to analyze these data. The variable log (month + 1) was used because log (month) is undefined when month is 0, and log (month + 1) yields the value 0 at baseline. The fitted values from the model were used to obtain the percentage change during the period of interest. Data on bone mineral density from the mixed-model analyses are presented unless otherwise specified. Role of the Funding Source Data were collected by investigators at each study site with the support of Merck Research Laboratories, Rahway, New Jersey. Analyses were performed by statisticians at Merck & Co., Inc. Data were interpreted by the authors, who submitted the manuscript for publication. Results Patient Characteristics and Retention Baseline randomization characteristics did not differ between participants who entered the extension phase and those who did not. Baseline demographic characteristics of the 244 women who entered the extension phase were s

Stimulation of undermineralized matrix formation by 1,25 dihydroxyvitamin D3 in long bones of rats

SummaryWe previously reported that pharmacologic doses of 1,25 dihydroxyvitamin D3 (1,25-(OH)2D3) given for 2–3 days, inhibited osteoblastic collagen synthesis in young rats. In this study, we tested the effects of 5, 25, and 125 ng of 1,25(OH)2D3 injected subcutaneously into 6-week-old rats for 12 or 18 days. In rats given 125 ng, cortical bone of distal half femurs exhibited decreased calcium (Ca) content but dry weight and hydroxyproline (Hyp) content were no different from control. Trabecular bone Ca was not different from control but dry weight and Hyp were increased. When cortical and trabecular bone were combined, there was a decrease in Ca, an increase in Hyp, and a 50% decrease in Ca:Hyp. Fluorescent labels given after 8 days of treatment were either diffuse or absent in calcified sections from rats given 125 ng, indicating impaired mineralization. The 25 and 125 ng doses produced hypercalcemia with normal serum phosphate. There was a dose-related increase in serum immunoreactive bone gla protein (BGP) and serum 1,25(OH)2D3 and a decrease in serum 25 (OH)D3. At the 5 ng dose, no adverse effects were seen on body growth. With 25 ng and 125 ng, growth was inhibited. Increased serum urea nitrogen and histologic evidence of nephrocalcinosis occurred at the 125 ng dose. When 125 ng was given for 12 days and then withdrawn for 6 days, systemic toxicity decreased and bone Hyp and Ca increased so that Ca:Hyp remained low and comparable to that of rats treated with 1,25(OH)2D3 continuously We conclude that pharmacologic doses of 1,25(OH)2D3 stimulate trabecular bone matrix formation but produce impairment of mineralization, despite a high Ca×Pi product.

Hypercalcemia associated with increased circulating 1,25 dihydroxyvitamin D in a patient with pulmonary tuberculosis

SummaryStudies are described in a 53-year-old man with far-advanced pulmonary tuberculosis who developed transient increases in circulating 1,25 dihydroxyvitamin D (1,25(OH)2D) and hypercalcemia while on antituberculous treatment. Serial dilution of an extract of the patients serum obtained while he was hypercalcemic displaced [3H]-1,25(OH)2D3 from chick intestinal receptor in a manner identical to authentic 1,25(OH)2D3. Serum 25-hydroxyvitamin D (25OHD) was suppressed during the abnormal elevation of serum 1,25(OH)2D. It is concluded that tuberculosis is another chronic granulomatous disease in which hypercalcemia may result from abnormal metabolism of vitamin D.

Calcitonin: A general survey

Since the initial discovery of calcitonin, a considerable amount of information has been obtained concerning structure, function, secretion, and effects of the hormone from a number of species. The purpose of the present report is to review the studies of structure and function, the factors that influence secretion and synthesis, and the effects and mechanism of action of calcitonin. The clinical uses of the hormone and syndromes of calcitonin excess are discu,sed.

Normal Vitamin D and Mineral Metabolism in Essential Hypertension

The effects of dietary sodium upon serum and urinary calcium and selected vitamin D metabolites were studied in two groups (n = 10 each) of age and gender matched, white normotensive subjects and patients with normal-renin hypertension. Isocaloric diets were consumed on a metabolic ward with sequential daily sodium intake of 109 meq for 5 days and 9 meq and 259 meq for 6 days each. Values for serum and urinary calcium, phosphorus, magnesium and electrolytes, creatinine clearance, plasma immunoreactive parathyroid hormone, and serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were similar in both study groups on each diet. Measurements of plasma renin activity and serum aldosterone levels were higher in the hypertensive than in the normotensive group on each diet (p less than .05-.01). Serum 1,25-dihydroxyvitamin D and urinary calcium increased on the high sodium diet in the normotensive (p less than .05) and the hypertensive groups (p less than .01). When the data for normotensive subjects and hypertensive patients were pooled by gender, males had a 1 1/2 to 3 times the urinary calcium excretion than females, regardless of diet. The present study indicates that there are no differences in the selected components of calcium and vitamin D metabolism in response to sodium intake in patients with essential hypertension and normal plasma renin activity as compared to normal controls.

SARCOIDOSIS: CLINICAL STAFF CONFERENCE AT THE NATIONAL INSTITUTES OF HEALTH

Excerpt Dr. John P. Utz: When presenting a conference for our group at the National Institutes of Health, one gets caught on the horns of a dilemma. One horn is to select a subject in which we are ...