SHBG and polycystic ovary syndrome: Importantly, women with NIH-defined PCOS have two distinct PCOS subtypes with different genetic heterogeneity: one defined as a “reproductive” group (23% of cases), characterized by higher luteinizing hormone (LH) and sex hormone binding globulin (SHBG) levels with relatively low body mass index (BMI) and insulin levels; the other defined as a “metabolic” group (37% of cases), characterized by higher BMI, glucose and insulin levels, with lower SHBG and LH levels [38,43].