Male Infertility

Male infertility results from impaired sperm production, impaired sperm transport, abnormal ejaculation, or reduced sperm function. It is evaluated as part of a couple’s reproductive problem, not as an isolated diagnosis assigned from one semen result. The hypothalamic–pituitary–gonadal axis explains several clinical patterns. Hypothalamic GnRH stimulates pituitary LH and FSH. LH stimulates Leydig cells to produce testosterone, while FSH acts on Sertoli cells to support sperm development within the seminiferous tubules. Sertoli cells also produce inhibin B, which contributes negative feedback to FSH. High intratesticular testosterone is required for spermatogenesis; a normal serum testosterone level alone does not prove that the testes are producing sperm normally. Causes are often organized by where the reproductive process fails: - Pre-testicular causes reduce hormonal stimulation, such as hypothalamic or pituitary disease, hypogonadotropic hypogonadism, or hyperprolactinemia. - Testicular causes damage or impair sperm production, including Klinefelter syndrome, previous cryptorchidism, testicular infection, varicocele, chemotherapy, radiation, and other primary testicular disorders. - Post-testicular causes obstruct sperm transport or interfere with ejaculation, including vasal agenesis, vasectomy, ejaculatory-duct obstruction, anejaculation, and retrograde ejaculation. The distinction matters because treatment...