Background: The ketogenic diet remains a valuable therapeutic option for patients with intractable epilepsy. However no data are available for the influence of ketogenic diet on thyroid function in children.

Purpose: The aim of this study was to investigate the effects of ketogenic diet on thyroid functions.

Methods: Between 2011 and 2013, a total of 31 children who received aketogenic diet for a 6-month-period were enrolled in the study. Serum free thyroxine (fT4) and thyroid-stimulating hormone (TSH) levels were measured before and at first, third and sixth months of therapy. The data were compared to those of a matched group of 45 children with newly onset epilepsy from our previous study.

Results: While average serum fT4 concentrations at baseline were significantly lower in patients receiving ketogenic diet compared to controls (p = 0.012), TSH concentrations were similar between the 2 groups. Serum fT4 levels increased significantly at month 3 and month 6 when compared to month 1 measurements (p = 0.022 and p = 0.016, respectively). Serum TSH levels nonsignificantly increased in patients at the first month of ketogenic diet as compared to baseline levels (p = 0.754). A significantly reduced serum fT4 concentrations and increased TSH concentrations were found in the controls at month-6 (p = 0.026, p = <0.001, respectively).

Conclusion: The ketogenic diet has no deletorious effect on thyroid function in children with refractory epilepsy.