On the Actions of Crystalline Vitamin D(2) (calciferol) in Chronic Parathyroid Tetany.

Vitamin D has proved effective in raising the serum calcium and alleviating the symptoms of chronic parathyroprivic tetany in experimental animals (1, 2) and man (3, 4, 5). A number of factors including dosage (6, 7), and calciumphosphorus content of the diet (8), have been found to influence its effect, and where these have not been taken into consideration vitamin D has failed (9, 10). The possibility of toxicity and the point made by Shelling and his associates that it raises the serum inorganic phosphorus, has led some workers to question the advisability of using vitamin D in tetany (11, 12). In most studies on the actions of vitamin D, irradiated ergosterol (viosterol) has been used. In dealing with its physiological and toxic effects it must be borne in mind that irradiated ergosterol is not a simple solution of synthetic vitamin D but rather, a complex mixture of irradiated sterols, only one of which has antirachitic activity. Undoubtedly, some of the conflicting results obtained have been owing to the presence of sterols other than vitamin D. By means of newer chemical and physical methods, it has been possible to study the individual products of ergosterol irradiation. During the course of irradiation ergosterol undergoes a series of changes schematically represented below: