Response of 1α,25-Dihydroxyvitamin D3to Hypocalcemia in Human Subjects

Abstract
We determined the response of 1α,25-dihydroxyvitamin D3 after mithramycin-induced hypocalcemia in eight subjects with polyostotic Paget's disease of bone. Thirty-six hours after infusion of mithramycin (25 μg per kilogram), the average calcium declined from 9.9±0.14 (S.E.M.) to 8.0±0.19 mg per deciliter (P3 rose from 98±12 to 332±61 pM (P3 and changes in parathyroid hormone (correlation coefficient, r = +0.91) and phosphate (r=-0.96). The relatively rapid response of 1α,25-dihydroxyvitamin D3 to hypocalcemia occurs with a time course consistent with regulation by parathyroid hormone and phosphate. (N Engl J Med 299:437–441, 1978)