Polycystic ovary syndrome (PCOS) is one of the most common endocrinological disorders among women of reproductive age, with a prevalence ranging between 6–20 % worldwide (Safiri et al., 2022). PCOS is a complex syndrome characterized by oligo/anovulation, hyperandrogenism, and polycystic ovarian morphology, presenting heterogeneous clinical and biochemical features (Baracat et al., 2022, Turan et al., 2015a). This condition not only leads to infertility but is also associated with metabolic disturbances, obesity, insulin resistance, and, in the long term, cardiometabolic complications (Guan et al., 2022, Cena et al., 2020, Xu and Qiao, 2022).

In recent years, the role of chronic low-grade inflammation in the pathogenesis of PCOS has been increasingly emphasized (Rudnicka et al., 2021, Orisaka et al., 2023). Inflammatory processes contribute to a vicious cycle by exacerbating insulin resistance, which in turn is associated with hyperandrogenism and ovulatory dysfunction (Armanini et al., 2022). Therefore, inflammatory indices derived from hematological parameters have emerged as practical, low-cost, and potentially valuable additional biomarkers in clinical practice.

The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and particularly the systemic immune-inflammation index (SII) have been extensively investigated as indicators of inflammatory response across various disease groups (Wang et al., 2023). SII has been reported to hold prognostic value in a wide range of conditions, from cancers to cardiovascular diseases (Nøst et al., 2021, Gao et al., 2024). However, studies evaluating immuno-inflammatory differences among PCOS phenotypes remain limited, and the available findings are often conflicting. Some reports suggest that hyperandrogenic and insulin-resistant phenotypes exhibit higher levels of inflammatory indices, while others have failed to demonstrate consistent differences (Kheirollahi et al., 2025). This inconsistency may be explained by variations in study design, sample size, or the heterogeneity of diagnostic criteria used across populations. Furthermore, most available studies have compared women with PCOS to healthy controls, whereas few have directly examined inter-phenotypic variations. Therefore, additional research focusing on phenotype-specific inflammatory profiles is warranted to clarify the role of immune-inflammatory indices in the heterogeneous presentation of PCOS and to determine their potential clinical utility in risk stratification and treatment planning (Moin et al., 2022).

The aim of this study was to compare hematological immune-inflammatory indices (NLR, PLR, MLR, and SII) across different PCOS phenotypes and to evaluate their potential utility as biomarkers in distinguishing phenotypic variations. Furthermore, it is anticipated that the findings of this research will contribute to a better understanding of the heterogeneous clinical nature of PCOS and support the development of phenotype-specific diagnostic and therapeutic strategies.