Calciferols vitamin 1,25-dihydroxycholecalciferol

The term vitamin D is used for a range of compounds which possess the property of preventing or curing rickets. They include ergocalciferol (calciferol, vitamin D ), chole-calciferol (vitamin Dg), dihydrotachysterol, alfacalcidol (la-hydroxycholecalciferol) and calcitriol (1,25-dihydroxycholecalciferol). 

Physiological forms of vitamin D include vitamin D2 (calciferol, ergocalciferol), vitamin D3 (cholecalciferol), phosphate esters of D2, D3, 25-hydroxycholecalciferol, 1,25-dihydroxycholecalciferol, and 5,25-dihydroxychole-calciferol. Vitamins D2 and D3 are 9,10-secosteroids that differ stmcturally in the degree of saturation of an... 

Nomenclature. Vitamin D all steroids with chole-calciferol-like biological activity cholecalciferol (vitamin D3) 25-hydroxycholecalciferol (calcidiol) la,25-dihydroxycholecalciferol (calcitriol). 

Miravet, L., J. R. Del, M. Carre, M. L. Queille, and P. Bordier The Biological Activity of Synthetic 25,26-Dihydroxycholecalciferol and 24,25-Dihydroxychole-calciferol in Vitamin D-Deficient Rats. Calcif. Tiss. Res. 21, 145 (1976). 

Vitamin D is composed of a number of related stmc-tures but the two most prominent members of the family are colecalciferol and ergocalciferol, which is formed from ergosterol rather than 7-dehydrocholesterol. Cole-calciferol is transformed into the most active form of the vitamin, 1,25-dihydroxycholecalciferol, by hydroxylation at the 25 position in the liver and finally at the 1 position in the kidneys. 

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