The two groups are comparable in age and BMI. However, higher levels of LH (t = 6.166, P = 0.000), total testosterone (Z =  − 5.535, P = 0.000), TSH (Z =  − 2.130, P = 0.033), platelet count (t = 2.607, P = 0.010), lymphocyte count (t = 2.199, P = 0.029), homocysteine (Z =  − 3.517, P = 0.000), ALT (Z =  − 2.436, P = 0.015), and uric acid (t = 3.715, P = 0.000) were identified in lean PCOS; FSH level was significantly lower in in lean PCOS as expected (t =  − 2.199, P = 0.029). The gene discussed is BRD2; the disease is polycystic ovary syndrome.