Background/aim: This study aims to investigate the association between polycystic ovary syndrome (PCOS) and obesity and insulin resistance (IR) with respect to anti-Müllerian hormone (AMH), inhibin A (INH-A), inhibin B (INH-B), and insulin-like peptide 3 (INSL3) levels, all factors which may have an impact on IR.Materials and methods: In this cross sectional study, 52 adolescent girls diagnosed with PCOS[groups:nonobese (NO), n = 23; overweight/obese (OW/O), n = 29] were included. Blood samples were obtained to measure AMH, INH-B, INH-A, and INSL3 levels, together with hormonal and biochemical assessments. Oral glucose tolerance test (OGTT) was performed and the indexes of IR [homeostasis model assessment: insulin resistance (HOMA-IR) and Matsuda index] were calculated.Results: Insulin resistance was 56.5% with OGTT and 30.4% with HOMA-IR in nonobese-PCOS girls. There was a correlation between INH-A and HOMA-IR even when controlled for body mass index (BMI). INH-B and FAI also had correlations with HOMA-IR which disappeared when controlled for BMI. In regression analyses, AMH (odds ratio = [0.903, P = 0.015) and FAI (odds ratio = 1.353, P = 0.023) are found to be contributors to IR. Their effect was BMI-independent. In ROC analysis, the cutoff value for FAI was 5.93 (sensitivity 71%) to define IR in PCOS girls.Conclusion: AMH and FAI may contribute to IR (defined by OGTT) in PCOS. FAI might be used as a supporting IR marker (defined by OGTT) in adolescent girls with PCOS.