Thyroid Hormone Metabolism During Liver Regeneration in Rats

The metabolism of thyroid hormones was studied during the prereplicative period of liver regeneration. After partial hepatectomy, serum thyroxine (T₄) and triiodothyronine (T₃) levels progressively fell, and reached a nadir at 12 h proportional to the quantity of liver tissue excised. The diminution (60-80/) in serum iodothyronines was related specifically to partial hepatectomy because laparotomy, ether anesthesia, and other stressful surgical procedures did not induce similar changes. At least 3 phenomena appear to be involved: 1) increased utilization and turnover of thyroid hormone by the regenerating liver remnant, 2) diminished hormone secretion by the thyroid gland between 6-12 h after surgery, and 3) a slightly 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. It is suggested, however, that additional unknown factors control increased hepatic thyroid hormone turnover after partial hepatectomy. (Endocrinology98: 1241, 1976