Vitamin D status in primary hyperparathyroidism: a Southern European perspective.

BACKGROUND: Vitamin D deficiency (VDD) is common in patients with primary hyperparathyroidism (pHPT), and this could affect the clinical expression of the disease. However, few North American or North European studies have addressed this issue, showing vitamin D repletion in only about one-third of the patients. SUBJECTS AND METHODS: Vitamin D status was evaluated both in an observational study in a series of 206 consecutive patients with pHPT at diagnosis and in a case-control analysis with 113 age- and sex-matched healthy blood donors. Vitamin D status was assessed by measuring plasma 25-hydroxy-vitamin D (25OHD) levels and was defined as VDD or severe VDD if 25OHD was <20 ng/ml (<50 nm) and <10 ng/ml (<25 nm), respectively.
RESULTS: No seasonal variability was observed in 25OHD levels. VDD was observed in 75 of 206 patients (36·4%). The VDD was severe in 24 of 75 patients (11·7%). There was no difference in prevalence of VDD between men and women nor between asymptomatic and 'bone and stone' symptomatic patients. 25OHD levels was negatively correlated with parathyroid hormone, ionized calcium, and bone turnover markers, and positively correlated with phosphate. 25OHD levels were also positively correlated with bone mineral density at all sites measured. In the case-control study, the overall prevalence of VDD and severe VDD was higher in patients with pHPT compared with controls (33·6% vs 10·6%, P < 0·0001, and 8·8% vs 1·8%, P = 0·0337, respectively).
CONCLUSIONS: Our study shows that VDD occurs in about one-third of patients with pHPT resident in a Southern European area, a lower figure than previously reported. Moreover, VDD is related to a more severe bone disease, and its prevalence is higher in patients with pHPT than in healthy matched subjects.