Thyroid function parameters and TSH in patients treated with anticonvulsant drugs

Several antiepileptic drugs change the serum levels of thyroid hormones by different mechanisms, of these diphenylhydantoin being the most known. This study was carried out on 96 patients in order to analyse the effects of long-term treatment with phenobarbital (N = 29), carbamazepine (N = 21), sodium valproate (N = 11), diphenylhydantoin (N = 6) and a combination of them all at therapeutic doses. We observed a decrease of T4 seric levels and free T4 index (in 25 and 14 patients respectively, under normal levels) free T4 normal, T3 normal, decreased rT3, and normal TSH in all groups being more noticeable in patients treated with diphenylhydantoin, carbamazepine, phenobarbital and lastly, sodium valproate. It is a different situation from a general non-thyroid disease, where there is a decrease of T3 and where the antiepileptic drugs of different chemical structure induce changes in seric levels of thyroid hormones. The basal TSH is the best measurement to reflect the euthyroidism of these patients.