Vitamin D status in Japanese patients with hyperparathyroidism: seasonal changes and effect on clinical presentation.

The disturbance of vitamin D metabolism plays an important role in determining the clinical presentation of hyperthyroidism. We studied 72 patients (65 women, 7 men) with primary hyperparathyroidism (pHPT). Clinical presentation, biochemical indices, and bone mineral density (BMD) were compared in three patient groups classified according to their serum 25-hydroxyvitamin D (25OHD) levels: 23 patients whose 25OHD level was <25 nmol/L comprised the low group, 26 whose level was 25 to 40 nmol/L made up the intermediate group, and 23 whose level was > 40 nmol/L comprised the high group. The mean serum calcium level was 10.8 +/- 0.9 mg/dl, and the mean weight of the resected parathyroids was 684 +/- 749 mg. The mean serum 25OHD level was 36.5 +/- 16.3 nmol/L (normal 25-100 nmol/L). Levels were below normal in 23 patients (32%). No between-group differences existed for clinical presentation, biochemistry, or BMD. Only differences in mean patient age were statistically significant between groups. Vitamin D deficiency is common among Japanese patients with pHPT, but the effects of HPT on clinical, biochemical, and densitometric indices are not pronounced. Our study population was at an early stage of pHPT, so the vitamin D deficiency may not be associated with the effects of HPT.