Suppression of Spermatogenesis by Exogenous Testosterone.

Sperm production starts from puberty in the seminiferous tubules providing testosterone production by the Leydig cells that takes place in the interstice of the testicles. Normal spermatogenesis depends on specific signalling from the hypothalamic-pituitary-gonadal axis. GnRH, FSH and LH are the main hormones involved in the production and maturation of spermatozoa. Exogenous administration of androgens influences the hypothalamic- pituitary-gonadal axis with negative feedback that may lead to a partial or complete cessation of spermatogenesis by decreasing FSH and LH. Despite the fact that many trials have confirmed that exogenous testosterone affects male fertility status, evidence regarding the long-term effects of treatment is conflicting. Regarding this aspect, many studies have confirmed a return to baseline sperm concentration after testosterone treatment discontinuation; however, none of them can specify how long recovery will take or whether the sperm count is sufficient for fertility.