Abstract
Summary The influence of a parathyroid hormone extract, calciferol and its related compounds on thyroxine secretion rate (TSR) of normal female mature rats was studied with the aid of 131I. Administration of 30 USP U of parathyroid extract/100 g BW/day for a period of 13 days induced a significant 21% increase in TSR associated with a slight increase in body weight. The TSR was increased 48%, 55%, and 103% respectively and accompanied by a dramatic loss of body weight when 200 /μg calciferol/100 g BW, 125 μg Hytakerol/100 g BW or 100 μg crystalline dihydrotachysterol/100 g BW were given daily for the same period.