A FASTING GLUCOSE TO INSULIN RATIO IS A USEFUL MEASURE OF INSULIN SENSITIVITY IN WOMEN WITH POLYCYSTIC-OVARY-SYNDROME

Women with polycystic ovary syndrome (PCOS) are profoundly insulin res istant, and the resultant hyperinsulinemia exacerbates the reproductiv e abnormalities of the syndrome. Agents that ameliorate insulin resist ance and reduce circulating insulin levels could provide a new therape utic modality for PCOS. Identifying the subset of PCOS women who are m ost insulin resistant may therefore be useful for selecting women who will respond to this therapy. We examined the correlation of basal and oral glucose-stimulated glucose and insulin levels and fasting and st imulated glucose/insulin (G:I) ratios with parameters of insulin sensi tivity obtained by frequently sampled iv glucose tolerance test (FSIGT ) to assess whether there is a simple screening test for insulin resis tance in PCOS. Forty PCOS women (aged 18-40 yr; body mass index, >26 k g/m(2)) and 15 control women matched for age, weight, and ethnicity un derwent both a 75-g oral glucose tolerance test (OGTT) and a FSIGT. Th e insulin sensitivity index (S-I) was calculated by application of the minimal model of glucose kinetics to the dynamics of plasma glucose a nd insulin levels during the FSIGT. The best correlation in PCOS betwe en S-I and a fasting level was found with fasting G:I ratios (r = 0.73 ; P < 0.0001). A less substantial, but significant, correlation was fo und with fasting insulin levels (r = 0.50; P < 0.001), and no signific ant correlation was found with fasting glucose levels (r = 0.24; P = N S). The fasting G:I was more strongly correlated with SI than with int egrated glucose and insulin responses during the OGTT. The only strong er correlation was with the OGTT 2 h G:I ratio (r = 0.74; P < 0.001). Stepwise regression analysis with S-I as the dependent variable and fa sting glucose and insulin levels, area under the curve for glucose and insulin, and a fasting G:I ratio showed that only the fasting G:I rat io was significantly predictive of S-I in the model (F to remove value = 38.1; P < 0.001). When viewed as a screening test for insulin resis tance in PCOS, setting a value of the fasting G:I ratio of less than 4 .5 as abnormal (using an S-I value below the 10th percentile of our co ntrol population as evidence for insulin resistance), the sensitivity of a fasting G:I ratio was 95%, the specificity was 84%, the positive predictive value was 87%, and the negative predictive value was 94%. R eceiver operator curve analysis showed that this fasting G:I ratio was the single best screening measure for detecting insulin resistance. W e conclude that a fasting G:I ratio may be useful as a screening test for insulin resistance in obese non-Hispanic white PCOS women. This ma y be a clinically useful parameter for selecting PCOS women most likel y to respond to therapeutic interventions that improve insulin sensiti vity.