Endocrinology of Male Infertility

Abstract

Understanding reproductive physiology is pivotal in the evaluation and therapy of endocrine abnormalities. Although an endocrinological cause of male infertility is uncommon (less than 2%) (1) identification is important, as specific hormonal therapy is often successful. The human testis is an organ of dual function: spermatogenesis, occuring in the seminiferous tubules, and secretion of steroid hormones (androgens) by the Leydig cells, present in the interstitial tissue. These testicular functions are intimately related, because testosterone synthesis is required not only for sperm production, but also for the development of secondary sexual characteristics and normal sexual behavior. The anterior pituitary controls both these functions through the secretion of gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). In turn, the anterior pituitary is regulated by the hypothalamic secretion of gonadotropinreleasing hormone (GnRH). The extrahypothalamic central nervous system then influences the hypothalamus. The hypothalamic-pituitary-gonadal axis consists of a closed-loop feedback control mechanism directed at maintaining normal reproductive function (Fig. 1) (2–5). Hypothalamic-pituitary-gonadal axis. LH, luteinizing hormone; FSH, follicle stimulating hormone; T, testosterone; DHT, dihydrotestosterone; E2, estradiol; GnRH, gonadotropin-releasing hormone; PR, prolactin; +, positive influence; −, negative influence. KeywordsLuteinizing HormoneSertoli CellLeydig CellSeminiferous TubuleCongenital Adrenal HyperplasiaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.