Insulin resistance and endocrine characteristics of the different phenotypes of polycystic ovary syndrome: a prospective study

BACKGROUND: Polycystic ovary syndrome (PCOS) is a heterogeneous disorder characterized by oligo- or anovulation (ANOV), biochemical or clinical manifestations of hyperandrogenemia (HA) and PCOs. Four phenotypes of PCOS exist [phenotype 1 (ANOV + HA + PCO), phenotype 2 (ANOV + HA), phenotype 3 (HA + PCO) and phenotype 4 (ANOV + PCO)] but the differences between them are not well studied. We compared markers of insulin resistance (IR) and endocrine characteristics between the different PCOS phenotypes. METHODS: We prospectively studied 1212 consecutive women with PCOS and 254 BMI-matched healthy women. RESULTS: Phenotypes 1-4 were present in 48.2, 30.7, 9.7 and 11.4% of patients, respectively. BMI did not differ between the four phenotypes and controls. Both normal weight and overweight/obese women with phenotypes 1 and 2 were more insulin resistant than controls. Overweight/obese, but not normal weight, women with phenotype 4 were more insulin resistant than controls, while IR in women with phenotype 3 did not differ from controls regardless of obesity. In normal weight subjects, women with phenotypes 1 and 2 were more insulin resistant than women with phenotype 4. In overweight/obese subjects, women with phenotype 1 were more insulin resistant than women with phenotypes 2 and 3 and women with phenotype 4 were more insulin resistant than those with phenotype 3. Circulating androgens were higher in normal weight and overweight/obese PCOS patients with phenotypes 1-3 compared with those with phenotype 4, and higher in normal weight PCOS patients with phenotype 1 than in those with phenotype 2. CONCLUSIONS: Phenotype 1 is associated with more IR and more pronounced HA than phenotype 2. Phenotypes 2 and 4 with obesity, are also characterized by IR. In contrast, phenotype 3 is not associated with IR.