1alpha-hydroxycholecalciferol in the treatment of hypoparathyroidism.

In two patients (father and daughter) with idiopathic hypoparathyroidism, one of whom was resistant to the action of vitamin D2 and AT-10, 1alpha-hydroxycholecalciferol (1alpha-(OH)D3) in doses of 2-5 mug/day restored the serum calcium concentration to the normal range. The calcemic effect of 1alpha (OH)D3 was in both patients due to an increased intestinal calcium absorption and increased calcium mobilization from bone. In one of the patients 1alpha-(OH)D3 also increased the renal tubular calcium reabsorption; in the other it did not have this effect, resulting in hypercalciuria as serum calcium rose. The lack of effect on tubular calcium reabsorption probably accounts for the relative resistance to the action of 1alpha-(OH)C3 in this patient compared with other.