Clinical Drug Experience Knowledgebase

Dihydrotachysterol (DHT) is a synthetic vitamin D analog activated in the liver that does not require renal hydroxylation like vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Dihydrotachysterol is used to treat hypocalcemia, hypoparathyroidism, and prevention of tetany. Dihydrotachysterol is hydroxylated in the liver to 25-hydroxy-dihydrotachysterol, which is the major circulating active form of the drug. Once hydroxylated to 25-hydroxy-dihydrotachysterol, the modified drug binds to the vitamin D receptor. The bound form of the vitamin D receptor serves as a transcriptional regulator of bone matrix proteins, inducing the expression of osteocalcin and suppressing synthesis of type I collagen. Dihydrotachysterol also increases renal phosphate excretion.   ^NCATS