Reproductive endocrine functions in men with primary hypothyroidism: effect of thyroxine replacement.

Reproductive endocrine functions were studied in men with primary hypothyroidism during the hypothyroid phase and after achieving euthyroid status with thyroxine substitution therapy. Hypergonadotropism [luteinising hormone (LH), 18.7 +/- 7.3 IU/l; follicle-stimulating hormone (FSH), 6.3 +/- 2.0 IU/l], low serum testosterone (6.1 +/- 2.8 nmol/l), low serum sex-hormone-binding globulin (SHBG; 13.2 +/- 2.0 nmol/l) and subnormal testosterone response to human chorionic gonadotropin hCG; (30% increase in serum testosterone following hCG) observed during the hypothyroid phase were restored to normal (LH, 7.2 +/- 2.0 IU/l; FSH, 2.7 +/- 0.9 IU/l; testosterone, 12.9 +/- 2.7 nmol/l; SHBG, 26.5 +/- 8.4 nmol/l, and 2-fold increase in serum testosterone following hCG) with thyroxine substitution therapy. Some improvement in sperm count and motility was also observed.