**2.5 Psychological stress**

Stress, in all its forms, is detrimental to male reproductive potential. The classical stress response activates the sympathetic nervous system and engages the cytothalamic-pituitary–adrenal (HPA) axis [15]. The HPA axis and gonadotrophininhibitory hormone (GnIH) have an inhibitory effect on testicular Leydig cells and the hypothalamic–pituitary-gonadal axis. This inhibitory effect reduces testosterone levels. This causes changes in the Sertoli cells and the blood-testicular barrier, which eventuallysuppress spermatogenesis [16].
