Supplementary thyroxine therapy in patients with hypothyroidism induced by long-term anticonvulsant therapy

Of 287 patients under long-term therapy with anticonvulsants, 24 with low serum thyroxine and free thyroxine concentrations were prescribed supplementary thyroxine in the present study. In addition, the basal metabolic rate (BMR) was measured in 13 out of 24 patients and in eight of them it was low (under -15%). Serum thyroid hormone concentrations improved after administration of thyroxine. However, improvement of the BMR was not obtained after one month of supplementary therapy. EEG after administration showed an increase in the power spectra of the occipital alpha 2 band (10.0-12.8 Hz) and beta 1 band (13.0-19.8 Hz), and a decrease in that of the theta band (4.0-7.8 Hz). The interpeak latency from wave I to wave V in the ABR was normalized after administration. These results suggest that supplementary therapy with thyroxine may be necessary in patients with hypothyroidism induced by anticonvulsants.