Neck circumference a good predictor of raised insulin and free androgen index in obese premenopausal women: changes with weight loss

OBJECTIVE Severe obesity can be associated with evidence of androgen excess and insulin resistance, which are features of the metabolic and polycystic ovary syndromes (PCOS). In this study, we examined the association between clinical and biochemical features of these syndromes and assess changes with weight loss. DESIGN A consecutive series of 107 severely obese premenopausal women presenting for obesity surgery. MEASUREMENTS Pre-operative assessment included details of clinical comorbidity, anthropometric measures and biochemical measures, including fasting insulin, glucose, lipid profile and sex hormone analysis. Changes in these measures for 42 of 52 (81%) patients at 1 year post surgery are reported. RESULTS Neck circumference and younger age were independent predictors of higher free androgen index (FAI) (combined r(2) = 0.36). If neck circumference is not included, then younger age, higher body mass index and raised fasting insulin levels were all independent predictors of FAI (r(2) = 0.29). Waist to hip ratio showed no predictive value (r = 0.14). Neck circumference was also a good clinical predictor of menstrual irregularity, hirsutism, infertility, insulin resistance and the PCOS. Neck circumference of less than 39, 39-42 and greater than 42 cm reflect a low, intermediate and high risk of the metabolic and PCOS syndromes in obese premenopausal women. For 42 patients who were followed for 1 year after surgery, the weight loss was associated with reduction of FAI, less insulin resistance and improved menstrual regularity and resolution of the PCOS in 11 of 12 cases. CONCLUSIONS Neck circumference is a good predictive measure of hyperinsulinaemia and raised androgens in obese premenopausal women. Weight loss following surgery improves ovarian function and vasculopathic risk.