Relationship among obesity, insulin resistance, and hyperinsulinemia in the polycystic ovary syndrome

Purpose: To evaluate the relationship between obesity and insulin resistance among women with polycystic ovary syndrome (PCOS) using a gold standard test.

Methods: A retrospective database analysis of 75 women with PCOS and 118 normal controls who underwent a modification of the insulin suppression test. The relationships between body mass index (BMI) and steady-state plasma glucose (SSPG) levels were investigated.

Results: Mean SSPG score for PCOS subjects was statistically similar than that of the controls at all BMI groupings. Only when PCOS subjects reached a BMI of ≥30 kg/m² that the PCOS subjects had higher mean SSPG score than the control subjects, although not significantly so (p = 0.07). The distribution of PCOS and control subjects in each SSPG quartile grouping was investigated. When comparing all PCOS and control subjects, PCOS subjects were more likely to be in the higher quartiles of SSPG score (p = 0.0001). However, when comparing the PCOS and control subjects, at each BMI grouping (<25, 25-29.9, and ≥30 kg/m²), there was no difference in the likelihood that a larger percent of subjects fell into a different quartile (p = 0.12, 0.69, 0.32, respectively).

Conclusions: PCOS subjects have increased magnitudes of insulin resistance when compared to ovulatory controls, when controlling for age, BMI, fasting glucose, and insulin levels. However, the magnitude of this insulin resistance in lean subjects is mild. Quantity of excess body fat, particularly subjects with a BMI of at least 30 kg/m² is the primary predictor of insulin resistance of sufficient magnitude to put PCOS subjects at increased risk for metabolic abnormalities.