1. Figure 1 The hypothalamic–pituitary–gonadal axis
Figure 1 | The hypothalamic–pituitary–gonadal axis. Secretion of the anterior pituitary gonadotropin hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are stimulated by the pulsatile release of gonandotropin- releasing hormone (GnRH) and inhibited by the release of gonadotropin-inhibiting hormone (GnIH) from the hypothalamus. Selective oestrogen receptor modulators (SERMs) competitively inhibit hypothalamic oestrogen receptors, which leads to increased anterior pituitary gonadotropin release and subsequent endogenous testosterone production. Inhibin B is secreted by the testicular germinal epithelium (primarily Sertoli cells) in response to FSH and subsequently acts on the anterior pituitary in a negative-feedback loop, inhibiting FSH production. Activin has an agonistic effect on the pituitary secretion of FSH and its release is inhibited by inhibin B. Aromatase inhibitors are used to correct a diminished testosterone:oestrogen ratio.
Kathrins, M. & Niederberger, C. (2016) Diagnosis and treatment of infertility-related male hormonal dysfunction
Nat. Rev. Urol. doi: /nrurol