Improvement in endocrine and ovarian function during dietary treatment of obese women with polycystic ovary syndrome.

OBJECTIVE: Obese women with polycystic ovary syndrome have a greater frequency of menstrual disturbance and of hirsutism than lean women with the syndrome. Initial studies have demonstrated a marked improvement in endocrine function following a short-term, very low calorie diet. The purpose of this study was to examine the effect of long-term calorie restriction on clinical as well as biochemical abnormalities in obese women with polycystic ovary syndrome.

DESIGN: We performed a within-group comparison of clinical and biochemical indices before and during dietary treatment.

PATIENTS: Twenty-four obese women with polycystic ovary syndrome (mean weight 91.5 (SD 14.7) kg) were scheduled for treatment for 6-7 months with a 1000 kcal, low fat diet. Nineteen of the 24 had menstrual disturbances, 12 had infertility and 19 were hirsute.

MEASUREMENTS AND RESULTS: Thirteen subjects lost more than 5% of their starting weight (range 5.9-22%). In this group there was no significant change in gonadotrophin or total serum testosterone levels but there was a marked increase in concentrations of sex hormone-binding globulin (pretreatment: 23.6 (9.5); post-treatment 36.3 (11.8) nmol/l, P = 0.002) and a reciprocal change in free testosterone levels (77 (26) vs 53 (21) pmol/l, P = 0.009). These changes were accompanied by a reduction in fasting serum insulin levels (median (range) 11.2 (5.2-32) vs 2.3 (0.1-13.8) mU/l, P = 0.018) and the insulin response to 75 g oral glucose. There were no significant changes in these indices in the group who lost less than 5% of their initial body weight. Of the 13 women who lost greater than 5% of their pretreatment weight, 11 had menstrual dysfunction. Amongst these women, nine of 11 showed an improvement in reproductive function, i.e. they either conceived (five) or experienced a more regular menstrual pattern. There was a reduction in hirsutism in 40% of the women in this group. By contrast, in the group who lost less than 5% of their initial weight, only one of the eight with menstrual disturbances noted an improvement in reproductive function and none had a significant reduction in hirsutism.

CONCLUSIONS: These data indicate that moderate weight loss during long-term calorie restriction is associated with a marked clinical improvement which reflects the reduction in insulin concentrations and reciprocal changes in SHBG. The improvement in menstrual function and fertility may therefore be consequent upon an increase in insulin sensitivity which, directly or indirectly, affects ovarian function.