Methods: In this retrospective study, the homeostasis model assessment for insulin resistance (HOMA-IR), prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), the LH:FSH ratio, and total testosterone and sex hormone-binding globulin (SHBG) were measured in 75 obese/overweight women with PCOS and insulin resistance before initiation of metformin treatment and after 6–8 months. Here, PRL is linked to polycystic ovary syndrome.