Vitamin D: the new functions of a former vitamin

Vitamin D has long been known for its anti-rachitic properties. Recent rese arch developements have pointed out its numerous in vitro and in vivo actio ns on the proliferation-differentiation of epidermal and cancer cells, as w ell as on the recruitment, differentiation and activities of the immune cel ls. Emerging evidence for associations between the genotype of the vitamin D receptor and the susceptibility to develop cancer, tuberculosis, or auto- immune diseases, brings further support to the physiological importance of these actions, although they do not seem to reflect as essential functions as the classical ones on calcium homeostasis and skeletal mineralization. N evertheless, these recently discovered actions have led to the development of new therapeutical tools for the treatment of psoriasis and investigation s are currently under way to evaluate the possible beneficial effects of th e active form of vitamin D, and of less hypercalcemic analogs, in patients with, or at risk for, colo-rectal, breast and prostate cancer in patients w ith autoimmune diseases, and for prolonging allograft survival.