Hormone Binding Globulins and Anticonvulsant Therapy

Serum sex hormone binding globulin, thyroxine binding globulin, cortisol binding globulin and vitamin D binding globulin, together with total levels of the appropriate bound hormones, were determined in 21 epileptic subjects who had been stabilised by long-term anticonvulsant therapy. Serum sex hormone binding globulin capacity was higher in these patients than in appropriate control groups (men p<0.05; women p<0.01), and values correlated with serum phenytoin levels in the female subjects (p<0.01). Thyroxine binding globulin levels were unaffected by anticonvulsants, but significant reductions in serum thyroxine (men p<0.05; women p<0.001) and triiodothyronine (men p<0.05; women p<0.01) were observed. Cortisol binding globulin capacity was appreciably elevated in patients of either sex (p<0.001), and in the women this was accompanied by a reduction in serum cortisol (p<0.001) and a significant correlation with the serum phenytoin concentration (p<0.01). Neither vitamin D binding globulin capacity nor serum 25-hydroxycholecalciferol levels were influenced by anticonvulsants in this study. It is concluded that anticonvulsant drug therapy causes widespread alterations in the normal homeostasis between hormones and their serum binding globulins. Such alterations may well have clinical significance.