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 less than 0.05; women p less than 0.01), and values correlated with serum phenytoin levels in the female subjects (p less than 0.01). Thyroxine binding globulin levels were unaffected by anticonvulsants, but significant reductions in serum thyroxine (men p less than 0.05; women p less than 0.001) and triiodothyronine (men p less than 0.05; women p less than 0.01) were observed. Cortisol binding globulin capacity was appreciably elevated in patients of either sex (p less than 0.001), and in the women this was accompanied by a reduction in serum cortisol (p less than 0.001) and a significant correlation with the serum phenytoin concentration (p less than 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.