The impact of gastric bypass surgery on sex hormones and menstrual cycles in premenopausal women.

Obesity has adverse effects on ovulation, menstrual cyclicity and oocyte development leading to clinical symptoms such as infertility and menstrual disorders. The Roux-en-Y gastric bypass (RYGB) leads to weight loss, improved insulin sensitivity and may improve ovarian function. In 31 premenopausal women, 18 eu- and 13 oligo-/amenorrhoic, we followed the changes in follicular phase sex hormones 3, 6 and 12 month after RYGB. The average weight loss during the first postoperative year was 39.6 kg. The insulin sensitivity and serum insulin improved markedly especially within the first three postoperative months. SHBG increased progressively and was doubled after 12 months. In contrast, total and free androgens and DHEA declined about 50% during the first three postoperative months and remained fairly constant hereafter. One year after surgery, 85% (11/13) of the women with oligo-/amenorrhea gained regular menstrual cycles. Our results indicate that some of the endocrine changes related to regulation of ovarian function occur very early after bariatric surgery.