Evaluation of Vitamin D Repletion Regimens to Correct Vitamin D Status in Adults

ObjectiveTo determine the efficacy and safety of commonly prescribed regimens for the treatment of vitamin D insufficiency.MethodsWe performed a retrospective analysis of 306 consecutive patients who were prescribed ergocalciferol (vitamin D₂) for correction of vitamin D insufficiency at the Atlanta Veterans Affairs Medical Center between February 2003 and May 2006. Serum levels of parathyroid hormone, 25-hydroxyvitamin D (25-OHD), and calcium were compared before and after treatment with ergocalciferol. Patients who did not have a 25-OHD determination (n = 41) were excluded from analysis. Vitamin D deficiency, insufficiency, and sufficiency were defined as a serum 25-OHD level of < 20 ng/mL, 21 to 29 ng/mL, and > 30 ng/mL, respectively.ResultsWe identified 36 discrete prescribing regimens. The 3 most common regimens were ergocalciferol 50,000 IU once weekly for 4 weeks followed by 50,000 IU once monthly for 5 months (n = 48); ergocalciferol 50,000 IU once monthly for 6 months (n = 80); and ergocalciferol 50,000 IU 3 times weekly for 6 weeks (n = 27). Each of these 3 treatments significantly increased serum 25-OHD (P < .01), but vitamin D sufficiency was achieved in only 38%, 42%, and 82% of study subjects, respectively. Regimens with > 600,000 IU of ergocalciferol given for a mean of 60 ± 40 days achieved sufficiency in 64% of cases, without vitamin D toxicity.ConclusionIn this study, regimens that contained at least 600,000 IU of ergocalciferol appeared to be the most effective in achieving vitamin D sufficiency. Guidelines for the treatment of vitamin D insufficiency in healthy adults should be developed. (Endocr Pract. 2009;15:95-103)     

Long-Term Bioavailability of Single Doses of Intramuscular Vitamin D2

Objective: We sought to determine the long-term bioavailability of single doses of intramuscular (IM) vita-min D₂ (D₂) in healthy adults.Methods: Forty healthy volunteers with hypovitaminosis D received a single dose of 200,000, 400,000, or 600,000 IU intramuscular D₂ or no treatment. Levels of 25-hydroxyvitamin D₂ (25&lsqb;OH]D₂) and 25-hydroxyvitamin D₃ (25&lsqb;OH]D₃) in serum were measured by liquid chromatography-tandem mass spectrometry. Vitamin D binding protein (DBP) and intact parathyroid hormone (iPTH), bone turnover markers (BTMs), and serum and urinary calcium were also measured.Results: After a single dose of D₂ injection, the level of 25(OH)D₂ increased slowly and reached a plateau at 8 weeks. The plateau remained stable for 12 weeks. The mean increase in 25(OH)D₂ was 6.8, 9.6, or 15.6 ng/mL after injection of 200,000 IU, 400,000 IU, or 600,000 IU D₂. Although endogenous 25(OH)D₃ levels were reduced by IM D₂, the total 25(OH)D levels increased by 5.0, 7.0, or 10.3 ng/mL in average after injection of 200,000 IU, 400,000 IU, or 600,000 IU D₂. The iPTH levels were also decreased by IM D₂. However, levels of serum calcium, BTMs, and DBP and urinary calcium were not altered by IM D₂.Conclusion: A single dose of 200,000 IU, 400,000 IU, or 600,000 IU IM D₂ raises total 25-hydroxyvitamin D levels by 5.0, 7.0, or 10.3 ng/mL on average for at least 12 weeks and reduces iPTH and endogenous 25(OH)D₃ levels without affecting levels of serum calcium, BTMs, DBP, and urinary calcium.     

Differencesin-Vitamin-D3-Dosing-Regimens in a Geriatric Community-Dwelling Population

ObjectiveThe adequate dose of vitamin D supple mentation for community-dwelling elderly people has not been thoroughly investigated. This study aims to determine the efficacy of a low-dose and a higher dose of vitamin D₃ in maintaining 25-hydroxyvitamin D [25(OH)D] levels at or above 30 ng/mL.MethodsThis was a single site, double-blind, ran domized exploratory clinical trial that enrolled adults 65 years of age and older. Within strata of baseline 25(OH) D levels (< 30 versus ≥ 30 ng/mL) subjects were random ized in a 1:2 ratio to receive either 400 or 2,000 IU vitamin D₃ daily for 6 months. The main outcome measures were changes in serum 25(OH)D levels according to baseline 25(OH)D levels and dose of vitamin D3.ResultsAt baseline, 41 of 105 participants (39%) had low 25(OH)D levels (< 30 ng/mL). After 6 months of vitamin D₃ supplementation, 21 of 32 participants (66%) receiving 400 IU and 14 of 59 participants (24%) receiving 2,000 IU of vitamin D₃ still had low 25(OH)D levels. Thelargest increases in serum 25(OH)D levels were observed in subjects with baseline levels < 30 ng/mL who received 2,000 IU of vitamin D daily.ConclusionRegardless of baseline 25(OH)D level, in persons 65 years of age and older, 6-month vitamin D₃ supplementation with 400 IU daily resulted in low 25(OH) D in most individuals, while 2,000 IU daily maintained 25(OH)D levels within an acceptable range in most people on this regimen. (Endocr Pract. 2012;18:847-854)     

Improvement in Pancreatic β-Cell Function with Vitamin D and Calcium Supplementation in Vitamin D-Deficient Nondiabetic Subjects

ObjectiveThere are varied reports on the effect of vitamin D supplementation on β-cell function and plasma glucose levels. The objective of this study was to examine the effect of vitamin D and calcium supplementation on β-cell function and plasma glucose levels in subjects with vitamin D deficiency.MethodsNondiabetic subjects (N = 48) were screened for their serum 25-hydroxyvitamin D (25-OHD), albumin, creatinine, calcium, phosphorus, alkaline phosphatase, and intact parathyroid hormone (PTH) status. Subjects with 25-OHD deficiency underwent a 2-hour oral glucose tolerance test. Cholecalciferol (9,570 international units [IU]/day; tolerable upper intake level, 10,000 IU/day; according to the Endocrine Society guidelines for vitamin D supplementation) and calcium (1 g/day) were supplemented.ResultsThirty-seven patients with 25-OHD deficiency participated in the study. The baseline and postvitamin D/calcium supplementation and the difference (corrected) were: serum calcium, 9 ± 0.33 and 8.33 ± 1.09 mg/dL (− 0.66 ± 1.11 mg/dL); 25-OHD, 8.75 ± 4.75 and 36.83 ± 18.68 ng/mL (28.00 ± 18.33 ng/mL); PTH, 57.9 ± 29.3 and 36.33 ± 22.48 pg/mL (− 20.25 ± 22.45 pg/mL); fasting plasma glucose, 78.23 ± 7.60 and 73.47 ± 9.82 mg/dL (− 4.88 ± 10.65 mg/dL); and homeostasis model assessment-2–percent β-cell function C-peptide secretion (HOMA-2–%B C-PEP), 183.17 ± 88.74 and 194.67 ± 54.71 (11.38 ± 94.27). Significant differences were observed between baseline and post-vitamin D/calcium supplementation serum levels of corrected calcium (Z, − 3.751; P < .0001), 25-OHD (Z, − 4.9; P < .0001), intact PTH (Z, − 4.04; P < .0001), fasting plasma glucose (Z, − 2.7; P < .007), and HOMA-2–%B C-PEP (Z, − 1.923; P < .05) as determined by Wilcoxon signed rank test. Insulin resistance as measured by HOMA was unchanged.ConclusionOptimizing serum 25-OHD concentrations and supplementation with calcium improves fasting plasma glucose levels and β-cell secretory reserve. Larger randomized control studies are needed to determine if correction of 25-OHD deficiency will improve insulin secretion and prevent abnormalities of glucose homeostasis. (Endocr Pract. 2014;20:129-138)     

Increase in Bone Mass After Correction of Vitamin D Insufficiency in Bisphosphonate-Treated Patients

ObjectiveTo assess the relative contribution of vitamin D insufficiency to loss of bone mineral density (BMD) in patients taking bisphosphonates.MethodsPatients were eligible for inclusion if they had osteoporosis or osteopenia and demonstrated a decline in BMD during the preceding year while taking stable doses of alendronate or risedronate, plus supplemental calcium and vitamin D. Patients with previously known secondary causes of osteoporosis were excluded from the study. Eligible patients underwent prospective measurement of bilateral hip and lumbar spine BMD by dual-energy x-ray absorptiometry, serum 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D, intact parathyroid hormone, osteocalcin, and thyroid-stimulating hormone (thyrotropin), and urinary calcium:creatinine ratio.ResultsAnnual BMD was assessed in 175 previously bisphosphonate-responsive patients with low BMD. Of the 175 patients, 136 (78%) had either a significant interval increase or no change in BMD, whereas 39 (22%) had a significant decrease. Of the 39 patients who lost BMD, 20 (51%) had vitamin D insufficiency (25-OHD < 30 ng/mL). After a single course of orally administered vitamin D₂ (500,000 IU during a 5-week period), the 25-OHD level returned to normal in 17 of the 20 vitamin D-insufficient patients and was associated with significant (P < .02) 3.0% and 2.7% increases in BMD at the lumbar spine and the femoral neck, respectively. Failure to normalize the serum 25-OHD level was associated with further loss of BMD.ConclusionVitamin D insufficiency was the most frequently identified cause of bone loss in patients with declining BMD during bisphosphonate therapy. Correction of vitamin D insufficiency in these patients led to a significant rebound in BMD. (Endocr Pract. 2008; 14:293-297)     

Abnormalities of Vitamin D and Calcium Metabolism after Surgical Treatment of Morbid Obesity: A Study of 136 Patients

ObjectiveTo assess the effect of bariatric surgical treatment of morbid obesity on bone mineral metabolism.MethodsWe analyzed pertinent vitamin D and calcium metabolic variables in 136 patients who had undergone a malabsorptive bariatric operation. Measurements of bone mineral density (BMD), serum 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D [1,25-(OH)₂D], parathyroid hormone (PTH), calcium, phosphorus, and alkaline phosphatase were performed. Statistical analyses assessed correlations among various factors.ResultsThe mean age (± SD) of the study group was 48.34 ± 10.28 years. Their mean weight loss was 114.55 ± 45.66 lb, and the mean duration since the bariatric surgical procedure was 54.02 ± 51.88 months. Seventeen patients (12.5%) had a T-score of -2.5 or less, and 54 patients (39.7%) had a T-score between –1.0 and –2.5. Of 119 patients in whom serum 25-OHD was measured, 40 (34%) had severe hypovitaminosis D (25-OHD < 8 ng/mL), and 50 patients (42%) had low hypovitaminosis D (serum 25-OHD 8 to 20 ng/mL). The magnitude of weight loss correlated negatively with serum 25-OHD, calcium, phosphorus, and calcium × phosphorus product values and positively with serum alkaline phosphatase level. Serum 25-OHD and calcium concentrations correlated positively with the BMD. PTH, serum 1,25-(OH)₂D, and alkaline phosphatase concentrations correlated negatively with the BMD, a reflection of the presence of secondary hyperparathyroidism, an accelerated conversion of 25-OHD to 1,25-(OH)₂D by the elevated PTH levels, and increased osteoblastic activity. The mean daily vitamin D supplementation was 6,472 ± 9,736 IU.ConclusionHypovitaminosis D and subsequent bone loss are common in patients who have undergone a bariatric surgical procedure for morbid obesity. These patients require rigorous vitamin D supplementation. (Endocr Pract. 2007;13:131-136)     

Plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol concentrations are decreased in hind limb unloaded Dahl salt-sensitive female rats

Plasma 1,25-dihydroxyvitamin D (1,25-(OH)₂D) concentration was shown to decrease during bed rest in several studies when baseline plasma 25-hydroxyvitamin D (25-OHD) concentration was sub-optimal. Dahl salt-sensitive female (S) rats, but not Dahl salt-resistant female (R) rats, demonstrated a 50% decrease in plasma 1,25-dihydroxycholecalciferol (1,25-(OH)₂D₃) concentration after 28 days of hind limb unloading (HU, disuse model) during low salt intake (0.3%). We tested the vitamin D endocrine system response of female S rats to hind limb unloading during high salt intake (2%, twice that of standard rat chow to mimic salt intake in the USA). Hind limb unloading resulted in lower plasma 25-OHD₃ concentrations in S-HU rats than in R-HU rats (P < 0.05) and greater urinary loss of 25-OHD₃ by S-HU rats than by S rats (P < 0.05). Plasma 1,25-(OH)₂D₃ concentration of S-HU rats was half that of S rats, but was unchanged in R-HU rats. The association of low plasma 25-OHD concentration with decrease in plasma 1,25-(OH)₂D concentration of hind limb unloaded rats and of bed rest participants (published studies) suggests that low vitamin D status might be a risk factor for decrease in plasma vitamin D hormone concentration during long-term immobilization or bed rest.     

The Vitamin D Dose Response in Obesity

ObjectiveThe prevalence of vitamin D inadequacy is high in obese individuals. Determining the response of serum 25-hydroxyvitamin D (25[OH]D) to vitamin D₃ supplementation in obese and nonobese individuals may lead to concurrent recommendations for optimal vitamin D intake in these populations. The objective of this study was to determine the dose response of vitamin D₃ in subjects with a body mass index ≥ 35 kg/m².MethodsRandomized, double-blind, placebo-controlled study. This study is an extension of our previous study of vitamin D dosing in healthy adults. After an assessment of baseline 25(OH)D levels, participants were randomized to a vitamin D supplementation arm (100 μg daily if baseline 25[OH]D was < 50 nmol/L, or 50 μg daily if baseline 25[OH]D was ≥ 50 nmol/L) or placebo arm. Subjects with baseline 25(OH)D level ≥ 80 nmol/L were excluded from the study. Two months following randomization, a repeat 25(OH)D measurement was done.ResultsFinal analysis included 25 subjects (14 placebo, 11 active). At 2 months, serum 25(OH)D concentration increased to a mean of 75 nmol/L in the active group. Mean slope (i.e., vitamin D₃ response), defined as 25(OH) D change/baseline dose, was 0.398 nmol/L/μg/day.ConclusionThe dose response of vitamin D₃ (slope) in obese subjects was significantly lower (P < .03) at 0.398 nmol/L/μg/day compared to the slope in the previous study of healthy subjects (0.66 nmol/L/μg/day). These results suggest that obese individuals may require 40% higher vitamin D intake than nonobese individuals to attain the same serum 25(OH)D concentration. (Endocr Pract. 2014;20:1258-1264)     

Seasonal Variation Of Vitamin D And Serum Thyrotropin Levels And Its Relationship In A Euthyroid Caucasian Population

Objective: It is unclear whether seasonal variations in vitamin D concentrations affect the hypothalamo-pituitary-thyroid axis. We investigated the seasonal variability of vitamin D and serum thyrotropin (TSH) levels and their interrelationship.Methods: Analysis of 401 patients referred with nonspecific symptoms of tiredness who had simultaneous measurements of 25-hydroxyvitamin D3 (25&lsqb;OH]D3) and thyroid function. Patients were categorized according to the season of blood sampling and their vitamin D status.Results: 25(OH)D3 levels were higher in spring-summer season compared to autumn-winter (47.9 ± 22.2 nmol/L vs. 42.8 ± 21.8 nmol/L; P = .02). Higher median (interquartile range) TSH levels were found in autumn-winter (1.9 &lsqb;1.2] mU/L vs. 1.8 &lsqb;1.1] mU/L; P = .10). Across different seasons, 25(OH)D3 levels were observed to be higher in lower quartiles of TSH, and the inverse relationship was maintained uniformly in the higher quartiles of TSH. An independent inverse relationship could be established between 25(OH)D3 levels and TSH by regression analysis across both season groups (autumn-winter: r = -0.0248; P<.00001 and spring-summer: r = -0.0209; P<.00001). We also observed that TSH varied according to 25(OH)D3 status, with higher TSH found in patients with vitamin D insufficiency or deficiency in comparison to patients who had sufficient or optimal levels across different seasons.Conclusion: Our study shows seasonal variability in 25(OH)D3 production and TSH secretion in euthyroid subjects and that an inverse relationship exists between them. Further studies are needed to see if vitamin D replacement would be beneficial in patients with borderline thyroid function abnormalities.Abbreviations: 25(OH)D2 = 25-hydroxyvitamin D2; 25(OH)D3 = 25-hydroxyvitamin D3; AITD = autoimmune thyroid disease; FT4 = free thyroxine; TFT = thyroid function test; TSH = thyrotropin; UVB = ultraviolet B     

Vitamin D-Binding Protein in Healthy Pre- and Postmenopausal Women: Relationship with Estradiol Concentrations

Objective: To examine the relationship between endogenous serum estradiol and vitamin D–binding protein (DBP) and total, free, and bioavailable 25-hydroxyvitamin D (25OHD) concentrations in pre- and postmenopausal women.Methods: In 165 healthy women (ages, 26 to 75 years) not taking any form of exogenous estrogen, the serum concentrations of estradiol, 25OHD, DBP, parathyroid hormone, and albumin were measured. Free and bioavailable 25OHD (free + albumin-bound) levels were calculated from total 25OHD, DBP, and serum albumin levels.Results: Premenopausal women had higher serum 25OHD (31.5 ± 7.9 ng/mL), DBP (45.3 ± 6.2 mg/dL), and estradiol (52.8 ± 35.0 pg/mL) levels than postmenopausal women (26.5 ± 4.9 ng/mL, 41.7 ± 5.7 mg/dL, and 12.9 ± 4.9 pg/mL), respectively. In addition, the calculated free and bioavailable 25OHD levels were higher in prethan postmenopausal women (P<.05). Serum estradiol correlated with DBP (r = 0.22; P<.01) and total 25OHD (r = 0.27; P<.01). In multivariate regression models (with or without serum 25OHD), estradiol was independently associated with DBP (P<.05).Conclusion: Lower estradiol level is one of the factors that contribute to lower DBP levels in older women. Our data indicate that besides well-known factors such as age, gender, and race, serum estradiol concentrations are also a physiologic predictor of DBP concentration.Abbreviations: 25OHD = 25-hydroxyvitamin D BMI = body mass index CV = coefficient of variation DBP = vitamin D–binding protein PTH = parathyroid hormone SHBG = sex hormone–binding globulin     

Vitamin D insufficiency in diabetic retinopathy

ObjectiveTo assess the relationship between vitamin D status and diabetic retinopathy.MethodsA clinic-based, cross-sectional study was conducted at Emory University, Atlanta, Georgia. Overall, 221 patients were classified into 5 groups based on diabetes status and retinopathy findings: no diabetes or ocular disease (n = 47), no diabetes with ocular disease (n = 51), diabetes with no background diabetic retinopathy (n = 41), nonproliferative diabetic retinopathy (n = 40), and proliferative diabetic retinopathy (PDR) (n = 42). Patients with type 1 diabetes and those taking > 1,000 IU of vitamin D daily were excluded from the analyses. Study subjects underwent dilated funduscopic examination and were tested for hemoglobin A_1c, serum creatinine, and 25-hydroxyvitamin D [25(OH)D] levels between December 2009 and March 2010.ResultsAmong the study groups, there was no statistically significant difference in age, race, sex, or multivitamin use. Patients with diabetes had lower 25(OH)D levels than did those without diabetes (22.9 ng/mL versus 30.3 ng/mL, respectively; P < .001). The mean 25(OH)D levels, stratified by group, were as follows: no diabetes or ocular disease = 31.9 ng/mL; no diabetes with ocular disease = 28.8 ng/mL; no background diabetic retinopathy = 24.3 ng/ mL; nonproliferative diabetic retinopathy = 23.6 ng/mL; and PDR = 21.1 ng/mL. Univariate analysis of the 25(OH) D levels demonstrated statistically significant differences on the basis of study groups, race, body mass index, multivitamin use, hemoglobin A_1c, serum creatinine level, and estimated glomerular filtration rate. In a multivariate linear regression model with all potential confounders, only multivitamin use remained significant (P < .001).ConclusionThis study suggests that patients with diabetes, especially those with PDR, have lower 25(OH)D levels than those without diabetes. (Endocr Pract. 2012; 18:185-193)     

Supplemental vitamin D increases serum cytokines in those with initially low 25-hydroxyvitamin D: A randomized,double blind,placebo-controlled study

The purpose of this study was to determine if vitamin D status before supplementation influences the cytokine response after supplemental vitamin D. Forty-six reportedly healthy adults (mean(SD); age, 32(7) y; body mass index (BMI), 25.3(4.5) kg/m²; serum 25-hydroxyvitamin D (25(OH)D), 34.8(12.2) ng/mL) were randomly assigned (double blind) to one of three groups: (1) placebo (n = 15), or supplemental vitamin D (cholecalciferol) at (2) 4000 (n = 14) or (3) 8000 IU (n = 17). Supplements were taken daily for 35 days. Fasting blood samples were obtained before (Baseline, Bsl) and 35-days after (35-d) supplementation. Serum 25(OH)D, 1,25-dihydroxyvitamin D (1,25(OH)D), cytokines, and intact parathyroid hormone with calcium were measured in each blood sample. Supplemental vitamin D increased serum 25(OH)D (4000 IU, ≈29%; 8000 IU, ≈57%) and 1,25(OH)D (4000 IU, ≈12%; 8000 IU, ≈38%) without altering intact parathyroid hormone or calcium. The vitamin D metabolite increases in the supplemental vitamin D groups (n = 31) were dependent on initial levels as serum 25(OH)D (r = −0.63, p < 0.05) and 1,25(OH)D (r = −0.45, p < 0.05) at Bsl correlated with their increases after supplementation. Supplemental vitamin D increased interferon (IFN)-γ and interleukin (IL)-10 in subjects that were vitamin D insufficient (serum 25(OH)D < 29 ng/mL) compared to sufficient (serum 25(OH)D ⩾ 30 ng/mL) at Bsl. We conclude that supplemental vitamin D increase a pro- and anti-inflammatory cytokine in those with initially low serum 25(OH)D.     

Treatment with 50000 IU Vitamin D2 Every Other Week and Effect on Serum 25-Hydroxyvitamin D2, 25-Hydroxyvitamin D3, and Total 25-Hydroxyvitamin D in Aclinical Setting

ObjectiveTo examine the effect of 50 000 IU-vitamin D₂ supplementation in a clinical setting on serum total 25-hydroxyvitamin D (25[OH]D), 25-hydroxyvitamin D₂ (25[OH]D₂), and 25-hydroxyvitamin D₃ (25[OH]D₃).MethodsThis retrospective cohort study was performed in an urban tertiary referral hospital in Boston, Massachusetts. Patients who had been prescribed 50 000 IU vitamin D₂ repletion and maintenance programs were identified through a search of our electronic medical record. Baseline and follow-up total serum 25(OH)D, 25(OH)D₂, and 25(OH)D₃ levels were compared.ResultsWe examined the medical records of 48 patients who had been prescribed 50 000 IU vitamin D₂ in our clinic. Mean ± standard deviation baseline total 25(OH) D was 31.0 ± 10.6 ng/mL and rose to 48.3 ± 13.4 ng/mL after treatment (P <.001). 25(OH)D₂ increased from 4.2 ± 4.3 ng/mL to 34.6 ± 12.3 ng/mL after treatment (P <.001), for an average of 158 days (range, 35-735 days). Serum 25(OH)D3 decreased from 26.8 ± 10.8 ng/mL to 13.7 ± 7.9 ng/mL (P <.001).ConclusionsFifty thousand IU vitamin D₂ repletion and maintenance therapy substantially increases total 25(OH)D and 25(OH)D2 despite a decrease in serum 25(OH)D3. This treatment program is an appropriate and effective strategy to treat and prevent vitamin D deficiency.(Endocr Pract. 2012;18:399-402)     

Low Free (But Not Total) 25-Hydroxyvitamin D Levels in Subjects with Normocalcemic Hyperparathyroidism

Objective: Normocalcemic primary hyperparathyroidism (NPHPT) is characterized by elevated parathyroid hormone (PTH) levels with persistently normal calcium levels. The diagnosis of NPHPT assumes the absence of secondary causes of elevated PTH levels. The objective of the current study was to examine levels of free 25-hydroxyvitamin D (25&lsqb;OH]D) in NPHPT subjects and healthy controls.Methods: Ten NPHPT subjects and 20 controls who were age, sex, race, and body mass index (BMI) matched were examined. The diagnosis of NPHPT was made if subjects had (1) a serum calcium level of 8.6 to 10.4 mg/dL, total 25(OH)D 30 to 40 ng/mL, and intact PTH (iPTH) ≥66 pg/mL; and (2) normal renal and liver function. Serum total 25(OH)D levels were measured by radioimmunoassay, and free 25(OH)D levels were determined using an enzyme-linked immunoassay.Results: Mean age of NPHPT subjects was 59.9 ± 5.4 years, and mean BMI was 28.4 ± 2.3 kg/m², which was not significantly different from the mean age and BMI of the control subjects. Mean total 25(OH)D level was 31.9 ± 1.7 ng/mL in NPHPT subjects and did not differ from that of the controls (32.7 ± 3.3 ng/mL; P = .52). However, mean free 25(OH)D was 5.0 ± 0.9 pg/mL in NPHPT subjects, which was 20% lower compared to the mean of the controls (6.2 ± 1.3 pg/mL; P = .013). Serum iPTH levels were inversely correlated with levels of measured free 25(OH)D (r = -0.42; P<.05) but did not correlate with levels of total 25(OH)D (r = -0.14; P>.10).Conclusion: Measured free 25(OH)D levels are lower in NPHPT subjects than in healthy control subjects. We suggest that some NPHPT subjects may actually have secondary hyperparathyroidism based on their free 25(OH) D levels.Abbreviations: 25(OH)D = 25-hydroxyvitamin D; BMI = body mass index; CV = coefficient of variation; DBP = vitamin D–binding protein; iPTH = intact parathyroid hormone; NPHPT = normocalcemic primary hyperparathyroidism     

Vitamin D supplementation restores the blunted muscle protein synthesis response in deficient old rats through an impact on ectopic fat deposition

We investigated the impact of vitamin D deficiency and repletion on muscle anabolism in old rats. Animals were fed a control (1 IU vitamin D₃/g, ctrl, n=20) or a vitamin D-depleted diet (VDD; 0 IU, n=30) for 6 months. A subset was thereafter sacrificed in the control (ctrl6) and depleted groups (VDD6). Remaining control animals were kept for 3 additional months on the same diet (ctrl9), while a part of VDD rats continued on a depleted diet (VDD9) and another part was supplemented with vitamin D (5 IU, VDS9). The ctr16 and VDD6 rats and the ctr19, VDD9 and VDS9 rats were 21 and 24 months old, respectively. Vitamin D status, body weight and composition, muscle strength, weight and lipid content were evaluated. Muscle protein synthesis rate (fractional synthesis rate; FSR) and the activation of controlling pathways were measured. VDD reduced plasma 25(OH)-vitamin D, reaching deficiency (<25 nM), while 25(OH)-vitamin D increased to 118 nM in the VDS group (P<.0001). VDD animals gained weight (P<.05) with no corresponding changes in lean mass or muscle strength. Weight gain was associated with an increase in fat mass (+63%, P<.05), intramyocellular lipids (+75%, P<.05) and a trend toward a decreased plantaris weight (−19%, P=.12). Muscle FSR decreased by 40% in the VDD group (P<.001), but was restored by vitamin D supplementation (+70%, P<.0001). Such changes were linked to an over-phosphorylation of eIF2α. In conclusion, vitamin D deficiency in old rats increases adiposity and leads to reduced muscle protein synthesis through activation of eIF2α. These disorders are restored by vitamin D supplementation.     

Effect of Metformin Therapy on Vitamin D and Vitamin B12 Levels in Patients with Type 2 Diabetes Mellitus

ObjectiveTo determine the effect of metformin on 25-hydroxyvitamin D [25(OH)D] and vitamin B₁₂ levels in patients with type 2 diabetes mellitus.MethodsWe performed a retrospective review of medical records of patients treated between 2003 and 2009 at Loyola University Medical Center, Maywood, Illinois, in both ambulatory primary care and endocrinology clinics. The study cohort consisted of 706 patients with type 2 diabetes mellitus who were 20 to 93 years old (mean age, 63 ± 13) and had a mean body mass index of 33.1 kg/m². Of these patients, 42% were treated with metformin, and 34% had been diagnosed with osteoporosis or osteopenia.ResultsPatients taking metformin had statistically significant lower vitamin B₁₂ levels than those not receiving metformin (P < .0001; 95% confidence interval [CI] = − 220 to − 84 pg/mL). No statistically significant difference was found between users and nonusers of metformin in regard to 25(OH)D levels when adjusted for variables (P = .297; 95% CI for mean difference = − 0.7 to 2.2 ng/mL). Metformin use did not adversely affect successful treatment of vitamin D deficiency in this patient population as a whole, nor did it affect the subgroup with osteoporosis (P = .956). The patients with osteoporosis had statistically significant lower baseline 25(OH)D levels in comparison with those without osteoporosis, when adjustments were made for all variables (P = .003; 95% CI = 0.7 to 3.5 ng/ mL).ConclusionThis study confirms the higher prevalence of vitamin B₁₂ deficiency in metformin-treated patients with type 2 diabetes than in those not treated with metformin. This study also suggests that vitamin D deficiency is not a clinical concern among metformin-treated patients with type 2 diabetes and that metformin does not negatively affect treatment of vitamin D deficiency in these patients. (Endocr Pract. 2012;18:179–184)     

Measurement of 25-OH-vitamin D in human serum using liquid chromatography tandem-mass spectrometry with comparison to radioimmunoassay and automated immunoassay

The plasma 25-OH vitamin D concentration is a reliable biomarker for vitamin D status but assay's variability makes adequate monitoring of vitamin D status difficult. We employed isotope-dilution liquid chromatography (LC) tandem-mass spectrometry (MS/MS) for the measurement of both 25-OH vitamin D₃ and 25-OH vitamin D₂ in human serum. Hexadeuterium labelled 25-OH vitamin D₃ internal standard (IS) was added to calibrators (prepared in phosphate-buffered saline with 60 g/L albumin), controls or patient sera and 25-OH vitamin D metabolites were released from vitamin D binding protein by adding sodium hydroxide prior to protein precipitation by acetonitrile/methanol (9:1, v/v). Subsequent off-line solid-phase extraction was followed by chromatographic separation on a C-18 column using a water/methanol/ammonium acetate gradient. Detection was by Atmospheric Pressure Electrospray Ionisation (AP-EI) followed by selected reaction monitoring. We compared the LC-MS/MS assay to the DiaSorin radioimmunoassay (RIA) and a recently re-standardised version of an automated electrochemiluminescent immunoassay (ECLIA) from Roche Diagnostics. We also analysed external quality control samples from the International Vitamin D External Quality Assessment Scheme (DEQAS) for comparison with other participating laboratories using LC-MS. The method was linear from 5 to at least 550 nmol/L with intra- and interday CV's ≤6% for both 25-OH vitamin D₃ and 25-OH vitamin D₂. Recoveries ranged between 94.9 and 106.9% for 25-OH vitamin D₃ and 82.7 and 100.3% for 25-OH vitamin D₂. Our results for the DEQAS serum pools averaged ?7.2% from the overall LC-MS method mean. The DiaSorin RIA agreed well with the LC-MS/MS method (r² = 0.90; average bias 1.61 nmol/L), the Roche ECLIA considerably disagreed (r² = 0.58; bias 10.13 nmol/L). This LC-MS/MS method is reliable and robust for the measurement of both 25-OH vitamin D₃ and 25-OH vitamin D₂ in human serum.     

Optimization and kinetic study on the synthesis of palm oil ester using Lipozyme TL IM

Enzymatic synthesis of palm oil esters (POE) was carried out via alcoholysis of palm oil (PO) and oleyl alcohol (OA) catalyzed by Lipozyme TL IM. The optimum reaction conditions were: temperature: 60 °C; enzyme load: 24.7 wt%; substrate ratio: 1:3 (PO/OA), impeller speed: 275 rpm and reaction time: 3 h. At the optimum condition, the conversion of POE was 79.54%. Reusability study showed that Lipozyme TL IM could be used for 5 cycles with conversion above 50%. The alcoholysis reaction kinetic follows the Ping-Pong Bi-Bi mechanism characterized by the V_max, K_m(PO), and K_m(OA) values of 32.7 mmol/min, 0.3147 mmol/ml and 0.9483 mmol/ml, respectively. The relationship between initial reaction rate and temperature was also established based on the Arrhenius law.     

Ethnicity,Clothing Style,and Body Mass Index are Significant Predictors of Vitamin D Insufficiency in Germany

ObjectiveTo analyze risk factors for vitamin D insufficiency in Germany with respect to ethnicity, sex, and clothing style.MethodsWe analyzed the routine diagnostic workups of 1,231 adult (45.9 ± 17.9 years old) German (n = 1,034) and Turk residents (n = 197) referred with nonspecific symptoms to the Thyroid Centers at St. Elisabeth-Hospital in Dorsten, Germany and Bottrop, Germany to assess for metabolic diseases. All subjects underwent a routine examination that consisted of a questionnaire, lab tests for 25-hydroxyvitamin-D (25OHD), and thyroid profile. Turk females with traditional clothing (headscarf and covered legs and arms) were considered to wear “covered clothing.” Logistic-regression was performed to identify factors that could predict vitamin D deficiency (< 20 ng/ mL) and insufficiency (20-30 ng/mL).ResultsVitamin D insufficiency was seen in 33% of Germans and 74.1% of Turks, and vitamin D deficiency was present in 11.3% and 44.2% of Germans and Turks, respectively (P < .001). The mean 25OHD value in Turk females with covered clothes was lower than that in Turk females with conventional clothing (16.3 ± 12.3 vs. 27.2 ± 15.8, P < .001). Vitamin D insufficiency was present in 86.0% of Turk females with covered clothing versus 62.8% with conventional clothing (odds ratio [OR] = 3.6, P = .002). Ethnicity, body mass index (BMI), and clothing style were significant predictors of vitamin D deficiency and insufficiency by logistic regression (P < .001).Conclusions(1) Vitamin D insufficiency among Turk residents in Germany is higher compared to Germans. The highest prevalence was present in Turk females with covered clothing. (2) Monitoring vitamin D in Turk residents in Germany is warranted. (3) Vitamin D supplements and access to facilities with sunlight exposure for females with covered clothing and all individuals with poor diets or limited access to sun exposure may prevent future health burden due to vitamin D insufficiency. (Endocr Pract. 2015; 21:122-127)