Thyroid activity in response to some gonadal steroids in methallibure-treated Heteropneustes fossilis (Bloch)

Methallibure treatment is as effective as hypophysectomy in reducing thyroid activity in H. fossilis. Sex steroids (TP and EB) administration restored thyroid activity in methallibure-treated females to normal level, but failed to elicit any response in males. This drug seems to block TSH secretion and thyroid hormone synthesis in H. fossilis.