Insulin-like peptide 5 is associated with insulin resistance in women with polycystic ovary syndrome

Insulin-like peptide 5 (INSL5) plays an important part in metabolic processes in vitro and in vivo. We hypothesized that INSL5 levels are associated with the presence of polycystic ovary syndrome (PCOS) and insulin resistance (IR). Circulating INSL5 levels were measured by an enzyme-linked immunosorbent assay in the PCOS group (n = 101) and control (n = 78) groups. The relationship between INSL5 and IR was evaluated by using regression models. The levels of circulating INSL5 were elevated in the individuals with PCOS (P < 0.001) and significantly associated with homeostasis model assessment of insulin resistance (HOMA-IR, r = 0.434, P < 0.001; HOMA-IS, r = 0.432, P < 0.001; QUICKI, r = −0.504, P < 0.001). The subjects in the highest tertile of INSL5 levels were more likely to have PCOS (odds ratio: 12.591, 95 % confidence interval 2.616–60.605) as compared with the lowest tertile after adjustment for potential confounders. Furthermore, the multiple linear regression analyses after adjustment for confounders showed an independent association between INSL5 levels and HOMA-IR (β = 0.024, P < 0.001). Circulating INSL5 concentration is linked to PCOS, possibly through increased insulin resistance.