Excretion of labeled thyroxine in the presence of cholesterol-cholic acid supplements.

Abstract

The addition of cholesterol and cholic acid to a purified iodine deficient diet for rats greatly increased the degree of thyroid enlargement. Measurement of fecal and urinary radioactivity after injection of I131-labeled thyroxine demonstrated an increased fecal excretion of activity in the cholesterol-cholic acid supplemented group. Since the thyroid enlargement is prevented by iodine supplementation, the cholesterol-cholic acid supplement is thought to accentuate iodine depletion either by increasing biliary excretion of thyroxine or by interfering with the intestinal reabsorption of thyroxine. The addition of cholesterol and cholic acid to a purified iodine deficient diet for rats greatly increased the degree of thyroid enlargement. Measurement of fecal and urinary radioactivity after injection of I131-labeled thyroxine demonstrated an increased fecal excretion of activity in the cholesterol-cholic acid supplemented group. Since the thyroid enlargement is prevented by iodine supplementation, the cholesterol-cholic acid supplement is thought to accentuate iodine depletion either by increasing biliary excretion of thyroxine or by interfering with the intestinal reabsorption of thyroxine.