Yves COMBARNOUS

Introduction Reproductive cycles in vertebrates are regulated by the hypothalamus. The secretion of gonadotropin releasing hormone (GnRH) stimulates the pituitary gland to release the gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH) (Licht, 1980; Kang et al., 2020). Gonadotropins (GTH) are composed of a common α-subunit, and a unique β-subunit with a biological role specific to each hormone (Aizen et al., 2007a; Aizen et al., 2007b).

Introduction After its isolation and identification in the pineal gland of the cow, in subsequent years melatonin was identified in a wide variety of animals and plants (1–7). The extensive distribution of melatonin, especially in the primitive bacteria (cyanobacteria and α-proteobacteria) indicates that the chemical is an ancient molecule that has been retained throughout the evolution of all organisms (8, 9) (Figure 1).