Table 2.

Summary of Effects of Hormonal Suppression on Protection and Stimulation of Gonadal Functions

Species	Effects of Hormonal Suppression in Males	Effects of Hormonal Suppression in Females
Mouse	Pretreatment suppression does not protect endogenous spermatogenesis. Suppression moderately enhances spermatogenesis from transplanted spermatogonia. Posttreatment suppression slightly stimulates recovery from surviving stem cells	Mixed results on protection of primordial follicles from cyclophosphamide. No protection of primordial follicles from radiation.
Rat	Pretreatment and posttreatment suppression markedly stimulate spermatogenic recovery from stem cells. Suppression markedly enhances spermatogenesis from transplanted spermatogonia	Mixed results on maintenance of primordial follicle number during prolong GnRH agonist treatment (independent of cytotoxic exposure). GnRH agonist, but not progestin, partially protects primordial follicles from irradiation damage.
Non-human primate	Neither pretreatment nor posttreatment suppression enhance recovery of spermatogenesis after irradiation.	Prolonged GnRH agonist treatment maintains primordial follicle numbers during cyclophosphamide treatment but no proof of protection against cyclophosphamide-induced damage. Suppression offers no protection from radiation-induced loss of primordial follicles.
Human	Suppression before and during therapy fails to protect spermatogenesis from damage from cancer chemotherapy or radiotherapy (6 studies). Suppression with testosterone before and during therapy protected spermatogenesis from damage from cyclophosphamide (1 study). Delayed posttreatment suppression failed to restore spermatogenesis.	Several non-randomized studies (some with concurrent controls) indicate that suppression markedly protects against premature ovarian failure. One small randomized study showed no protective effect of suppression.