Thyroid function during B-vitamin supplementation of patients on antiepileptic drugs

Objectives: Patients on antiepileptic drugs (AEDs) may have low serum concentrations of thyroxine, with or without a compensatory increment in thyroid-stimulating hormone (TSH). Furthermore, patients on AEDs often have hyperhomocysteinemia and low concentrations of vitamins B-6, B-2 and folate. Previously, an inverse relationship between thyroxine and homocysteine concentrations has been observed. In animals, deficiency of vitamin B6 has been found to impair the hypophyseal release of TRH. We have studied the effect of B-vitamin supplements on thyroid function in patients on AEDs. Design and methods: Thirty-two patients on AEDs were identified with hyperhomocysteinemia and low folate, B6 and B2. They were supplemented with pyridoxine, riboflavin and folic acid for 30 days. Results: At baseline, the patients had low serum concentrations of free thyroxin and slightly elevated TSH. On day 30 of the B-vitamin supplements, homocysteine had decreased, however, the thyroid parameters remained unchanged. Conclusions: Hyperhomocysteinemic patients on AEDs have indications of hypothyroidism, however, supplementation with B-vitamins does not improve their thyroid function. (C) 2006 The Canadian Society of Clinical Chemists. All rights reserved.