Obesity and Insulin Resistance, Not Polycystic Ovary Syndrome, Are Independent Predictors of Bone Mineral Density in Adolescents and Young Women

Introduction: Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders that affects females of reproductive age. The characteristic features of PCOS individually have opposing effects on bone mineral density (BMD); however, their cumulative effect on BMD has not been clearly defined. Adolescence and young adulthood span a crucial period in achieving peak bone mass. Thus, a better understanding of the impact of PCOS on BMD in this age group is needed. Objectives: To determine whether BMD is different between young females with PCOS and controls and to identify factors that influence BMD in this population. Methods: Data from four cross-sectional studies with a total of 170 females aged 12–25 years with PCOS (n = 123) and controls (n = 47) with a wide range of BMIs (18.7–53.4 kg/m²) were analyzed. Participants had fasting glucose, insulin, and free and total testosterone concentrations measured. HOMA-IR was calculated. Whole-body BMD was assessed by dual-energy X-ray absorptiometry. Multiple regression analysis for predicting BMD included PCOS status, menstrual age, obesity, HOMA-IR, and free testosterone. Results: HOMA-IR and total and free testosterone were significantly higher in PCOS compared to controls but there was no difference in BMD z-score between PCOS (0.8 ± 1.0) and controls (0.6 ± 1.0) (p = 0.36). Obesity (p = 0.03) and HOMA-IR (p = 0.02) were associated with BMD z-score. Conclusions: Obesity status and insulin resistance, but not PCOS status, were each independently associated with BMD in adolescents and young women who spanned a wide range of BMIs.