Evaluation of subclinical hypothyroidism in ambulatory children with controlled epilepsy on valproate monotherapy.

There are conflicting reports in the literature about the influence of valproate on thyroid function. A cross-sectional study was performed to determine the prevalence of subclinical hypothyroidism in ambulatory children aged 3 to 15 years with controlled epilepsy receiving valproate monotherapy for at least 6 months. Fifty-seven consecutive children with controlled epilepsy on valproate monotherapy and 52 healthy age- and sex-matched control children were studied. Thyroid-stimulating hormone, free thyroxine, antithyroid peroxidase antibodies, and serum valproic acid levels were measured. There was a significantly high (P = .012) prevalence of subclinical hypothyroidism (26%) in those receiving valproate monotherapy compared with healthy controls (7.7%). Median duration of valproate therapy was significantly higher (P = .039) in the subclinical hypothyroidism group (21 months, range 6-36) compared with those without subclinical hypothyroidism (14 months, range 6-25). Results of the present study suggest higher prevalence of subclinical hypothyroidism in children with controlled epilepsy on long-term valproate monotherapy.