Antithyroid Action of Ketoconazole: In-vitro Studies and Rat In-vivo Studies

Inspection of the chemical structure of ketoconazole indicates that it may have antithyroid activity. The antithyroid action of this drug was demonstrated in-vitro and in-vivo. In-vitro, it was found to form a complex with iodine (formation constant Kc 141 L mol-1), and to inhibit lactoperoxidase (IC50 2 x 10(-4) M). Its effects in-vivo in the rat were assessed by assay of circulating-thyroxine, and from the histological appearance of the thyroid gland. Thyroid gland weight was increased in rats treated with ketoconazole.