Obesity and its role in polycystic ovary syndrome

To examine the mechanism by which obesity influences ovulation, 55 patients with oligo- or anovulation were studied. Parameters measured in serum were sex steroid-binding globulin (SSBG), testosterone (T), PRL, LH, FSH, and estradiol (E2). The women were divided into 2 groups: an obese group (group 1), greater than 145% of ideal body weight, and a normal weight group, less than 120% ideal body weight. SSBG was measured by saturation analysis T, LH, FSH, PRL, and E2 were measured by RIA. SSBG group 1 levels were 7.14 ng dihydrotestosterone bound/ml compared to 14.7 ng dihydrotestosterone bound/ml in group 2 (P less than 0.05). There were no significant differences in FSH, T, or E2. The correlation of body weight vs. SSBG in all patients was r = -0.62. In these 2 groups, the SSBG was significantly lower in the obese patients compared to that in the normal weight patients, independent of T or E2 levels. SSBG correlated negatively with body weight, suggesting that obesity has an influence on SSBG levels independent of hormonal status. When SSBG is lowered, there may be an increase in free T which, by inhibiting follicular maturation, may begin the sequence of events seen in polycystic ovary syndrome.