To determine whether obesity-related reproductive endocrine abnormalities in ovulatory women are reversible with weight loss. Observational cohort study. Healthy volunteers in an academic research environment. Women aged 18-48 years with regular menstrual cycles 21-40 days and a body mass index (BMI) >or=35 kg/m(2) planning to undergo bariatric surgery were recruited. Twenty-five eumenorrheic (non-polycystic ovary syndrome) women with a mean BMI of 47.3 +/- 5.2 kg/m(2) were sampled with daily menstrual cycle urinary hormones before (n = 25) and 6 months after (n = 9) weight loss surgery resulting in >25% reduction of initial body weight. Daily hormones were compared before and after surgery and with 14 normal-weight control subjects. Metabolites of LH, FSH, E(2), and P were measured daily for one menstrual cycle. Group means were compared using t tests among ovulatory cycles. Luteal pregnanediol glucuronide (Pdg) increased from 32.8 +/- 10.9 to 73.7 +/- 30.5 microg/mg creatinine (Cr) and whole-cycle LH increased from 168.8 +/- 24.2 to 292.1 +/- 79.6 mIU/mg Cr after surgically induced weight loss. Luteal Pdg remained lower than in normal-weight control subjects (151.7 +/- 111.1 microg/mg Cr). Obese women took longer to attain a postovulatory Pdg rise of >2 microg/mg Cr than control subjects (3.91 +/- 1.51 vs. 1.71 +/- 1.59 days); this improved after surgery (2.4 +/- 1.82 days). Whole-cycle estrone conjugates (E(1c)) was similar to control subjects at baseline, but decreased after weight loss (from 1,026.7 +/- 194.2 to 605.4 +/- 167.1 ng/mg Cr). Follicle-stimulating hormone did not relate to body size in this sample. Women of very high BMI have deficient luteal LH and Pdg excretion and a delayed ovulatory Pdg rise compared with normal-weight women. Although these parameters improved with weight loss, Pdg did not approach levels seen in normal-weight women. Luteinizing hormone may be less effective in stimulating the corpus luteum in obesity. The large postoperative decrease in E(1c) may reflect the loss of estrone-producing adipose tissue after weight loss.
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