ABSTRACT
Spermatogenesis, the multistep process of producing haploid spermatozoa, is precisely regulated by consistent hormonal milieu. The process is initiated and maintained at a steady pace by the orchestration of endocrine, paracrine and autocrine factors. The hypothalamo-pituitary-gonadal (HPG) axis is the principal endocrine determinant of hormonal regulation of spermatogenesis with the gonadotropin-releasing hormone (GnRH) inducing gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These act on testicular cells, Leydig and Sertoli cells to mediate steroidogenesis and spermatogenesis. The testicular cell-to-cell communication defines the next level of intricate endocrine and paracrine cross-talks in the regulation of spermatogenesis. Steroidogenesis in the Leydig cells produces testosterone and its derivatives that diffuse in Sertoli cells to regulate spermatogenesis and aid estrogen production. Inhibin, activin, follistatin and estrogen produced by the Sertoli cells, in turn, operate the feedback regulation of GnRH, FSH, LH and testosterone. Besides the classical axes of hormonal regulation, various metabolic hormones, growth factors and local paracrine factors affect spermatogenesis either directly acting on the testicular cells or modulating the endocrine regulation. This chapter concisely presents the hormonal control of spermatogenesis individually addressing the prime endocrine players.
