OBJECTIVE: To assess the effects of age on the hormonal, metabolic, and ultrasonographic features of polycystic ovary syndrome (PCOS).DESIGN: Observational study.SETTING: University department of obstetrics and gynecology.PATIENT(S): Patients with PCOS (n = 1,212) and healthy women (n = 254).INTERVENTION(S): None.MAIN OUTCOME MEASURE(S): Differences in the hormonal, metabolic, and ultrasonographic features of PCOS between age groups.RESULT(S): A progressive decline in circulating androgens was observed with advancing age. Patients 21-30 years old had lower plasma glucose and insulin levels, lower area under the oral glucose tolerance test curve and lower homeostasis model assessment of insulin resistance index, and higher glucose/insulin and quantitative insulin sensitivity check index than patients 31-39 years old. The prevalence of PCOS phenotypes changed with age. More specifically, the distribution of the phenotypes did not differ substantially between patients ≤ 20 years old and patients 21-30 years old. However, a decline in the prevalence of phenotype 1 (characterized by anovulation, hyperandrogenemia, and polycystic ovaries) and an increase in the prevalence of phenotype 4 (characterized by anovulation and polycystic ovaries without hyperandrogenemia) were observed in patients 31-39 years old.CONCLUSION(S): In women with PCOS, hyperandrogenemia appears to diminish during reproductive life whereas insulin resistance worsens.