Tachysterol is one of several sterols derived from ergosterol by irradiation with ultraviolet light. Its relation to the other sterols can best be illustrated by the scheme modified by Bills1 from that of Setz:
Ergosterol Lumisterol Tachysterol Calciferol (vitamin D) Substance 248 (Toxisterol) Suprasterol I Suprasterol II Experimentally tachysterol has been found to cause an increase in absorption and urinary excretion of calcium, and a rise in the concentration of calcium in the serum. There is no evidence that parathyroid function is affected. An orally effective derivative, dihydrotachysterol (antitetanic preparation no. 10, or "A. T. 10"), was first used in the treatment of parathyroid tetany by Holtz,2 in Germany, in 1933. Since then it has been extensively used, chiefly in Germany, and its effects have been reported on in considerable detail. The literature has recently been reviewed by Albright and his associates.3 Fromtheir review the principal data concerning dihydrotachysterol may