BRD2 and hypogonadotropic hypogonadism: We surveyed articles in PubMed using the following keywords: ‘Sertoli cell’, ‘FSH’, ‘spermatogenesis’, ‘Sertoli cell proliferation’, ‘Sertoli cell differentiation’, ‘Spermatogonia stem cell self-renewal’, ‘meiosis’, ‘Spermatogonia proliferation’, ‘apoptosis’, ‘hypogonadotropic hypogonadism’, ‘normogonadotropic’, ‘FSH treatment’.