Changes in thyroid hormones following liver intoxication with carbon tetrachloride

The metabolism of thyroid hormones was studied after carbon tetrachloride (CCl4) liver damage. Thyroxine (T4) and triiodothyronine (T3) levels fell and reached a nadir in the first 24 hours after CCl4 administration. Thyroxine binding globulins (TBG) and thyroid stimulating hormone (TSH) also decreased, reaching their lower values in the same period. Blood and liver T4 turnover measured in CCl4 treated rats were faster than in control animals. Therefore, at least three phenomena appear to be involved after CCl4 intoxication in rats: (1) increased utilization and turnover of thyroxine by the regenerating liver; (2) diminished thyroid hormone secretion by the thyroid gland, and (3) reduced concentration of serum iodothyronine carrier proteins. The results support the concept that the liver participates in the metabolic regulation of T3 and T4 which, in turn, control hepatocellular growth.