Effect of gossypol on the thyroid in young rats.

The effect of gossypol on thyroid structure and function was examined. Groups of young male rats were subcutaneously injected daily with 0.2 ml gossypol acetic acid in doses of 1, 5, or 10 mg per kg body weight. Control rats were injected with vehicle only. At the end of the 15-day treatment, there was a dose-dependent decrease in the serum concentrations of thyroid hormones, i.e., free thyroxine, triiodothyronine, and reverse triiodothyronine. Histopathological examination revealed focal degeneration of thyroid follicles after a dose of 1 mg gossypol per kg body weight; widespread follicular atrophy occurred with 5 mg and 10 mg gossypol per kg body weight. The degenerating follicles were lined with discontinuous cuboidal or squamous follicular epithelium, some of which exfoliated into colloid.