Various neuroendocrine hormones secreted by the hypothalamic-pituitarygonadal (HPG) axis play a major role in human fertility. By regulating fertility, the HPG axis interacts with nutrition, food intake, body condition, stress and response to season or day length (Roberson et al. 2010). All of these factors must interact correctly to maintain fertility. Not surprisingly, given this complex mechanism, human infertility is frequent, affecting approximately 1 in 10 couples (Matzuk & Lamb 2002). Furthermore, approximately one third of cases of human male infertility remain unexplained (Moskovtsev et al. 2010)
