Effects of 12-month antiepileptic drug use on thyroid functions in children; A retrospective observational study

INTRODUCTION: The purpose of this study was to examine the effects of antiepileptics on thyroid function tests and to compare these effects among the different antiepileptics.
METHODS: Two hundred twenty patients (102 female and 118 male) aged 1-17 indicated for antiepileptic drug (AED) therapy for epilepsy were enrolled in this study performed in the pediatric neurology unit of a university hospital between January 2014 and January 2018. Patients using a single AED and with complete seizure control were included. During the study period, the local protocol required the systematic control of free thyroxine (fT4) and thyroid-stimulating hormone (TSH) levels at the beginning of treatment and at the 12th month of AED therapy.
RESULTS: The mean age of the patients was 10.2±4.4 years. TSH elevation was observed in only eight patients. These eight patients’ thyroid autoantibodies were negative and their thyroid USGs were normal. Subclinical hypothyroidism (TSH: 5-10, fT4 normal) was present in three of the eight patients, and these were therefore not started on medication. The other five were started on L-thyroxine. Four of these were using valproic acid and one was using carbamazepine. We found no significant difference between TSH and fT4 levels measured before the start and at the 12th month of drug therapy, nor among the AEDs.
DISCUSSION AND CONCLUSION: AEDs have no marked effects on thyroid function, and may therefore be safely used from that perspective.