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Primary hyperparathyroidism (PHPT) is associated with hypovitaminosis D as assessed by serum total 25-hydroxyvitamin D (TotalD) levels. The aim of this study is to evaluate whether this is also the case for the calculated bioavailable 25-hydroxyvitamin D (BioD) or free 25-hydroxyvitamin D (FreeD), and whether the vitamin D status is influenced by genetic background. We compared vitamin D status of 88 PHPT patients each with a matched healthy family member sharing genetic background, i.e., first-degree relative (FDR), or not, namely an in-law relative (ILR). We compared TotalD and vitamin D-binding protein (DBP), using the latter to calculate BioD and FreeD. We also genotyped two common DBP polymorphisms (rs7041 and rs4588) likely to affect the affinity for and levels of vitamin D metabolites. TotalD was lower (p < 0.001) in PHPT (12.3 ± 6.6 ng/mL) than either family member group (FDR: 19.4 ± 12.1 and ILR: 23.2 ± 14.1), whether adjusted for DBP or not. DBP levels were also significantly lower (p < 0.001) in PHPT (323 ± 73 mg/L) versus FDR (377 ± 98) or ILR (382 ± 101). The differences between PHPT and control groups for TotalD, BioD, and FreeD were maintained after adjustment for season, gender, and serum creatinine. 25-hydroxyvitamin D, evaluated as total, free, or bioavailable fractions, is decreased in PHPT. No difference was seen between first-degree relative and in-law controls, suggesting that neither genetic nor non-genetic background greatly influences the genesis of the hypovitaminosis D seen in PHPT.

Objective: To describe the biochemical effects of an over-supplementation of vitamin D3 in two patients with primary hyperparathyroidism (PHPT)., Design: Two patients (A and B) with PHPT took erroneously 2,400,000 U (300,000 U/day for 8 days) and 4,500,000 U (300,000 U/day for 15 days) of cholecalciferol, respectively. They were followed for 4 months and ionized calcium, creatinine, PTH, 25 hydroxy-vitamin D, 1,25(OH)₂D and urinary calcium/creatinine levels were measured. Finally, the patients were operated on and a parathyroid adenoma was removed in both., Results: One week after the last dose of vitamin D, serum ionized calcium (iCa) rose from 1.35 to 1.41 mMol/L (n.r. 1.14-1.31) for patient A, and from 1.43 to 1.62 for patient B, while fasting urinary Calcium/Creatinine (uCa/Cr) augmented from 0.31 to 0.50 mg/mg, and from 0.32 to 0.55, respectively. During the follow-up, the average levels of iCa were 1.37 ± 0.03 and 1.48 ± 0.07 mMol/L, while those of uCa/Cr were 0.29 ± 0.13 and 0.32 ± 0.13, both iCa and uCa/Cr levels returning to baseline values within 4 months., Conclusions: The unintentional over-supplementation of vitamin D in the two PHPT patients caused a moderate and temporary increase of hypercalcemia and hypercalciuria and was not associated with clinical signs of toxicity.

Aim: We investigated inpatients with and without Type 2 diabetes mellitus, aged over 60 yr, to compare their vitamin D status and calcium homeostatic parameters., Materials and Methods: We studied 140 patients consecutively admitted to our Internal Medicine Unit during the year 2010 (61 from November to April, 79 from May to October). The sample encompassed 70 patients with and 70 without diabetes. At admission we measured serum calcium (Ca), phosphate (P), sodium (Na), potassium (K), creatinine (Cr), alkaline phosphatase total activity (AP), albumin adjusted serum calcium (Caalb adj), 25 hydroxy-vitamin D (25OHD), PTH, and 24-h urinary Na/Cr (uNa/Cr), K/Cr (uK/Cr), Ca/Cr (uCa/Cr), P/Cr (uP/Cr) ratios, and calcium excretion (Ca ex)., Results: 25OHD levels of patients with and without diabetes did not significantly differ. In patients without diabetes recruited from November to April, 25OHD levels were significantly lower than those from May to October, whilst patients with diabetes did not show a significant seasonal variation. PTH had opposite non-significant seasonal variations, and negatively correlated with 25OHD in both groups of patients. This correlation was lost after adjusting for age and body mass index in patients with diabetes. These inpatients had higher serum P and lower uP/Cr, according to lower PTH. Their serum glucose negatively correlated with uCa/Cr and Ca ex, contrary to inpatients with other diseases. Instead, uCa/Cr and Ca ex correlated with uNa/Cr only in patients without diabetes., Conclusions: Inpatients with diabetes did differ from those with other disorders for vitamin D status and calcium-phosphate homeostatic mechanism.

Introduction: Previous papers investigating vitamin D status have often outlined the significant relationships between serum parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD), but the influence of ionized calcium levels has not been concomitantly considered., Design: Cross-sectional., Materials and Methods: In 1050 healthy men (547) and women (503), serum ionized calcium (iCa), creatinine (Cr), albumin, 25OHD, and PTH were measured. After conventional analysis, a regression tree was fitted on the data set., Results: 25OHD and PTH values showed significant opposite seasonal changes. 25OHD levels negatively correlated with PTH, which in turn negatively correlated with iCa. A regression tree was fitted to the whole data set using PTH as the response variable and 25OHD and iCa as covariates. PTH concentration depended on that of iCa only in subjects with 25OHD levels>16.35 ng/mL, while for 25OHD<16.35 ng/mL it depended on 25OHD values., Conclusions: Our results indicated that PTH levels were highly conditioned by those of 25OHD in subjects with 25OHD values lower than 16.35 ng/mL and by those of iCa only for higher 25OHD concentration., (Copyright 2010 Elsevier Inc. All rights reserved.)

Introduction: Recent sun exposure should correlate with circulating 25-hydroxyvitamin D [25(OH)D] due to ultraviolet B (UVB)-catalyzed cutaneous synthesis of vitamin D., Methods: A Sun Exposure Score was calculated for healthy adults using a recall questionnaire assessing daily Time in Sun (<5 min, 5-30 min, >30 min) and Skin Exposure (face/hands; face/hands and arms; face/hands and legs; and "bathing suit") for 1 week in each of the winter and summer (n=47 and 23, respectively; n=18 participated in both). Concentrations of 25(OH)D were measured by DiaSorin RIA on end-of-week sera., Results: Mean serum 25(OH)D was higher in summer than winter (58.6+/-16.5 nmol/L vs. 38.8+/-29.0 nmol/L, respectively, P=0.003 unpaired). The calculated Sun Exposure Score correlated strongly with serum 25(OH)D during summer (Spearman's rho=0.59, P=0.003); based on the Pearson coefficient of determination, summer Sun Exposure Score explained 38% of the variability in summer serum 25(OH)D. The Sun Exposure Score did not correlate with 25(OH)D in the winter (rho=0.19, P=0.210). The summer correlation was largely explained by the Time in Sun (rho=0.58, P=0.004) rather than area of Skin Exposed (rho=0.10, P=0.660). Although there was a correlation between winter and summer Sun Exposure Scores (rho=0.63, P=0.005), there was no summer vs. winter correlation in serum 25(OH)D (rho=0.08, P=0.76)., Conclusion: This simple 1-week sun exposure recall questionnaire predicted summer serum 25(OH)D concentrations, accounting for 38% of the variability in 25(OH)D among healthy Italian adults., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)