No effect of ketoconazole on thyroid function of normal subjects and hypothyroid patients

To investigate a possible inhibitory effect of the antifungal agent ketoconazole on thyroid function, five patients with hypothyroidism and ten normal subjects were treated with ketoconazole at high doses (600 mg/daily in three 20-mg oral doses) for four weeks. The thyroid-stimulating hormone (TSH), and also TT3, TT4, FT3 and FT4, were measured before and after the end of treatment. In all of the subjects of our study, both normal and hypothyroid patients no significant modifications of circulating thyroid hormones and TSH were detected. Both normal and hypothyroid subjects did not show clinical changes of thyroid function as compared with the basal condition. These findings do not support any inhibitory effect of ketoconazole on the synthesis of thyroid hormones and thyroid function.