Response of 1alpha,25-dihydroxyvitamin D3 to hypocalcemia in human subjects.
We determined the response of 1alpha,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 microgram per kilogram), the average calcium declined from 9.9 +/- 0.14 (S.E.M.) to 8.0 +/- 0.19 mg per deciliter (P less than 0.005). Serum parathyroid hormone increased from 122 +/- 6 to 226 +/- 36 microliter eq per milliliter (P less than 0.05), serum phosphate decreased from 3.8 +/- 0.11 to 2.9 +/- 0.14 mg per deciliter (P less than 0.005), and urinary cyclic 3,5'-adenosine monophosphate increased from 4.6 +/- 0.35 to 7.5 +/- 0.80 mumol per gram of creatinine (P less than 0.005). Serum 1alpha25-dihydroxyvitamin D3 rose from 98 +/- 12 to 332 +/- 61 pM (P less than 0.05), the increase following the changes in parathyroid hormone and phosphate by 12 to 24 hours. When this lag period was taken into account, there was a significant relation (P less than 0.01) between the increase in 1alpha,25-dihydroxyvitamin D3 and changes in parathyroid hormone (correlation coefficient, r = +0.91) and phosphate (r = -0.96). The relatively rapid response of 1alpha,25-dihydroxyvitamin D3 to hypocalcemia occurs with a time course consistent with regulation by parathyroid hormone and phosphate.
D000368:Aged; D002118:Calcium / Q000097:blood; D000242:Cyclic AMP / Q000652:urine; D004100:Dihydroxycholecalciferols / Q000097:blood*; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D006996:Hypocalcemia / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010001:Osteitis Deformans / Q000097:blood / Q000188:drug therapy; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000378:metabolism; D008926:Plicamycin / Q000494:pharmacology / Q000627:therapeutic use
D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D010281:Parathyroid Hormone; D010710:Phosphates; D000242:Cyclic AMP; D008926:Plicamycin; D002118:Calcium