[Vitamin D 1980--a stocktaking (author's transl)].

Vitamin D3 and its various metabolites have a central position in the regulation of the calcium- and phosphorus metabolism. Of special importance is 1,25-dihydroxyvitamin D3, which is almost exclusively synthesized in the kidney. Its production is dependent upon several hormonal stimuli and of course occurs normally only in intact renal tissue. The multifactorial regulation of its formation implies that a variety of diseases could cause disturbances in the metabolism of vitamin D. 1,25-dihydroxyvitamin D3 exerts its biological effects not only at the intestine, bone and kidney, but as well presumably in organs as the parathyroid glands, hypophysis, pancreas and skin. 24,25-dihydroxyvitamin D3--although its biological value is still in debate--represents possibly a second vitamin D-hormone of importance. Inspite of intensive research work the metabolic fate of vitamin D3 and its full biological significance is not yet entirely understood.