Vitamin D status in primary hyperparathyroidism

Background

Hypovitaminosis D worsens the manifestations of primary hyperparathyroidism (PHPT). Only a few studies have assessed the status of vitamin D in PHPT. The objective of this study was to determine the prevalence of 25(OH)D levels < 50 nmol/L in PHPT in comparison to a population without PHPT.

Methods

Subjects with PHPT were identified from the computerized database of the Clalit Health Services in Israel and were included only if they had an available serum 25(OH)D test result in 2009 and were not taking vitamin D supplements in 2008-2009 prior to the 25(OH)D test result. Subjects with renal failure were excluded (included n = 1180). All other subjects with an available 25(OH)D value in 2009 constituted the control group (n = 184,479).

Results

Subjects with PHPT and 25(OH)D < 50 nmol/L had higher levels of serum PTH, alkaline phosphatase, and calcium levels compared to those with 25(OH)D levels ≥ 50 nmol/L (P < 0.02). The mean serum 25(OH)D level was 47.7 ± 22.5 nmol/L compared to 52.1 ± 24.5 nmol/L in the control group (P < 0.001). 59.6% of subjects with PHPT had 25(OH)D levels < 50 nmol/L as compared to 49.5% in the control group (P < 0.001). Logistic regression, controlling for gender, ethnicity, age, and seasonality, showed that PHPT independently predicted 25(OH)D levels < 50 nmol/L; OR = 1.61(95% CI, 1.43-1.82).

Conclusions

Serum 25(OH)D levels < 50 nmol/L are frequent in PHPT, are more common than in controls, and are associated with more severe bone disease based on higher serum PTH and bone turnover biomarkers.