BRD2 and hypogonadotropic hypogonadism: We defined 4 groups according to the relative contribution of central and gonadal dysfunction based on FSH and INB levels: Group A: primary hypogonadism (FSH >15 IU/l and undetectable INB (<10 pg/ml); Group B: central hypogonadism (FSH <0.5 IU/l, INB <10 pg/ml); Group C: partial gonadal & central dysfunction (FSH 1.5–15 IU/l, INB >20 pg/ml); Group D: mild central and severe gonadal dysfunction (FSH 1.5–15 IU/l, INB < 10 pg/ml.