GCG and Insulin resistance: OGTT: oral glucose tolerance test; PCOS: polycystic ovary syndrome; ASRM-ESHRE: American Society for Reproductive Medicine-European Society of Human Reproduction and Embryology; BMI: body mass index; LDL: low-density lipoprotein; ELISA: enzyme-linked immunosorbent assay; cIMT: carotid intima-media wall thickness; RHI: reactive hyperemia; GLP-1: glucagon-like peptide 1; SHBG: sex hormone-binding globulin; HOMA-IR: homeostatic model assessment for insulin resistance