Effects of active vitamin D3 and parathyroid hormone on the serum osteocalcin in idiopathic hypoparathyroidism and pseudohypoparathyroidism.

Serum osteocalcin was measured in patients with idiopathic hypoparathyroidism or pseudohypoparathyroidism, before or during the treatment with active vitamin D3 (1,25(OH)2D3 or 1 alpha OHD3). Serum osteocalcin and plasma 1,25(OH)2D were decreased in 11 patients with idiopathic hypoparathyroidism before treatment (2.8 +/- 1.27 ng/ml, P less than 0.001 and 14.3 +/- 4.27 pg/ml, P less than 0.001, respectively). In 24 patients with idiopathic hypoparathyroidism during the treatment, serum osteocalcin and plasma 1,25(OH)2D were within the normal range (4.5 +/- 0.74 ng/ml and 25.7 +/- 5.69 pg/ml, respectively). In five patients with pseudohypoparathyroidism before treatment, plasma 1,25(OH)2D was decreased (15.6 +/- 10.6 pg/ml, P less than 0.001) but serum osteocalcin was normal (7.8 +/- 1.66 ng/ml). In nine patients with pseudohypoparathyroidism during the treatment with active vitamin D3, serum osteocalcin and plasma 1,25(OH)2D were normal (6.8 +/- 1.47 ng/ml and 27.2 +/- 6.0 pg/ml, respectively). Serum PTH in pseudohypoparathyroidism was increased before treatment (0.70 +/- 0.34 ng/ml, P less than 0.05) and was normal during the treatment (0.50 +/- 0.13 ng/ml). In idiopathic hypoparathyroidism, the active vitamin D3 increased serum osteocalcin without PTH. In pseudohypoparathyroidism, PTH may increase serum osteocalcin or modulate the effect of active vitamin D3 on serum osteocalcin.