Figure 5.

Regulation of the androgen (and estrogen) synthesis by the adrenal cortex and testes. Abbreviations: GnRH: gonadotropin-releasing hormone; CRH: corticotropin-releasing hormone; ACTH: corticotropin; (gonadotropins) FSH: follicle-stimulating hormone; LH: luteotropic hormone; E1: estrone; E2: 3,17β-estradiol; ABP: androgen-binding protein. The other abbreviations have been described in Figure 2. The solid black arrows show paths or relationships. The dotted black line depicts the brain modulation of steroid hormone synthesis by the brain through other additional means (i.e., nervous signals and non-steroidal hormones). The dashed black lines indicate the possibility of direct interchange of pools between tissue and blood. The green lines show stimulatory/activating effects, and the red lines inhibitory/deactivating effects. The effects of exogenous T (i.e., administered as a drug) on GnRH functions overall have been presented as a red dashed line to somehow differentiate it from the tissue-released T.