9, 10-Secoergosta-5, 7, 10(19), 22-tetraene-3, 25-diol. Biologically active metabolite of vitamin D2 which is more active in curing rickets than its parent. The compound is believed to attach to the same receptor as vitamin D2 and 25-hydroxyvitamin D3.

Biliary metabolite of vitamin D2 in chick.

Major circulating form of vitamin D in man.

Metabolite from serum of rats given large doses of vitamin D3.