Calcidiol

Calcidiol, calcifediol, 25-hydroxycholecalciferol, or 25–hydroxy–vitamin D, is a prehormone which is produced by the metabolism of vitamin D3  (cholecalciferol) and which is converted by the kidneys (via 25-Hydroxyvitamin D3 1-alpha-Hydroxylase) into calcitriol (1,25-vitamin D), a steroid hormone.

Clinical significance
In medicine, bloodstream concentration of calcidiol is commonly used to measure overall vitamin D levels. Calcifediol promotes the mineralization of bones and teeth and is used to treat diseases caused by vitamin D deficiency such as rickets and osteomalacia. It is effective even in azotemic patients.