Stimulating effect of thyroid hormone on insulin-like growth factor I release and synthesis by perfused rat liver.

The direct effect of thyroid hormone on insulin-like growth factor I (IGF-I) release and synthesis was investigated in perfused rat liver. Physiological doses (from 50 to 1000 ng/dl) of 3,5,3'-triiodothyronine administration in the perfusing medium increased IGF-I release and concentration in the perfused liver in a dose dependent manner. While physiological doses (from 2 to 10 micrograms/dl) of thyroxine did not affect the release and synthesis of IGF-I in the perfused liver. These results suggest that 3,5,3'-triiodothyronine, but not thyroxine, directly enhances the release and synthesis of IGF-I in a dose dependent manner in the rat liver.