Thyroid function in epileptic mothers and their infants at birth

It has been suggested that patients receiving anticonvulsant therapy have depressed thyroid function. Thyroid function was studied in 16 pregnant epileptic women who were receiving various anticonvulsants; 20 nonepileptic pregnant women served as controls. Maternal and umbilical cord blood was collected at delivery and serum thyrotropin, total thyroxine, triiodothyronine, triiodothyronine resin uptake, and free thyroxine levels were measured. The free thyroxine index was calculated from the thyroxine and triiodothyronine resin uptake data. There were no significant differences in any of the maternal parameters. In cord serum, the thyroxine level was significantly lower (p less than 0.001) in the infants of the epileptic mothers. The triiodothyronine resin uptake was slightly increased in the epileptic group (p less than 0.05) so that the free thyroxine index largely compensated for this. The thyrotropin, free thyroxine, and triiodothyronine levels did not differ between the two groups. Thus the low thyroxine values in cord blood of infants of epileptic mothers receiving anticonvulsants probably reflect an alteration in protein binding rather than a true alteration in thyroid function.