[Physiopathological and therapeutic aspects of vitamin D (author's transl)]

In the last decade our knowledge on vitamin D has grown considerably due to the identification of numerous steps of the vitamin D metabolism and to the isolation and synthesis of active metabolites. Therefore a lot of progress had been made in the understanding of the physiological mechanism of regulating blood calcium homeostasis and of the pathogenesis of many related diseases. The diseases connected to the calcium-phosphate metabolism requiring treatment with vitamin D and its metabolites are numerous. The basis for a rational therapeutic approach is provided by the new concepts on the pathogensis of the various diseases and on the pharmacology of vitamin D metabolites. Pure vitamin D depletion may be controlled with physiological doses of vitamin D. Administration of 25-OHD3 is advisable in chronic hepatitis or cirrhosis accompanied by a defect of 25-hydroxylation and/or intestinal loss of the metabolite. A defect in the synthesis of 1,25-(OH)2D3, the metabolite of renal origin, is present in an interesting and wide group of diseases. These are: chronic renal insufficiency, hypoparathyroidism, hypocalcemic D-resistant rickets and senile or post-menopausal osteoporosis. In the treatment of this group of diseases, which sometimes is of a preventive nature, it is preferable to administer the dihydroxylated metabolites of vitamin D. The results of treatments and prevention in a few selected conditions are reported.