Correlation between the thyrotropin-thyroxine resistance index and insulin resistance in polycystic ovary syndrome patients with phlegm-dampness syndrome

Introduction Polycystic ovary syndrome (PCOS) patients classified as the phlegm-dampness syndrome typically suffer from metabolic dysfunction mainly driven by insulin resistance (IR). Indices evaluating thyroid hormone responsiveness have emerged as promising biomarkers for metabolic disease research. However, limited research has investigated the thyrotropin-thyroxine resistance index (TT4RI), a marker quantifying central pituitary thyroid sensitivity, in this distinct PCOS subgroup. This study aimed to explore the association between TT4RI and IR in PCOS patients with phlegm-dampness syndrome. Methods We enrolled 486 PCOS patients with complete baseline data in the present study. Among them, 264 patients were diagnosed with PCOS accompanied by phlegm-dampness syndrome. The 264 patients were further subdivided into two subgroups: with IR (n=208) and without IR (n=56), and clinical indicators were compared between the two subgroups. We evenly stratified the 264 phlegm-dampness syndrome PCOS patients into three groups to perform intergroup comparisons. Spearman’s correlation and multivariate linear regression analyses were used to investigate the association. ROC curves were also employed to compare the discriminatory performance of TT4RI, thyroid-stimulating hormone index(TSHI), and FT3/FT4 in identifying insulin resistance in these patients(n=264). The sole primary outcome of this study was HOMA-IR. Results Relative to the subgroup without IR (n=56), the subgroup with IR (n=208) patients displayed significantly higher blood pressure, obesity-related anthropometric values, triglycerides (TG), fasting plasma glucose (FPG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR),free triiodothyronine (FT3), thyroid-stimulating hormone (TSH) and TT4RI (P<0.05).Patients in the high TT4RI tertile group exhibited a relatively more prominent phenotype of IR. TT4RI exhibited positive correlations with weight, body mass index (BMI), FPG, FINS, HOMA-IR, free thyroxine (FT4), and TSH (P<0.05).In the multiple linear regression model, after adjusting for age, BMI, systolic blood pressure(SBP) and SHBG, only a marginally significant association was observed between HTT4RI group and IR. ROC analysis indicates that TT4RI exhibits limited discriminatory performance for identifying IR among PCOS patients with phlegm-dampness syndrome. Conclusions Among phlegm-dampness syndrome PCOS women, diminished central pituitary thyroid hormone sensitivity is associated with increased insulin resistance. Further prospective research is needed to confirm these findings and explore clinical relevance.