ABSTRACT
We have come to realize that vitamin D is actually a prehormone, serving as the parent compound for the production of three active metabolites: 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, and 24,25-dihydroxyvitamin D3. This chapter summarizes evidence that all three metabolites produce physiological effects in vitro and in vivo, and where possible, discusses what is known about their receptors.
