[citation needed] The identity[5] of GnRH was clarified by the 1977 Nobel Laureates Roger Guillemin and Andrew V. Schally:[6] As is standard for peptide representation, the sequence is given from amino terminus to carboxyl terminus; also standard is omission of the designation of chirality, with assumption that all amino acids are in their L- form.
In mammals, the linear decapeptide end-product is synthesized from an 89-amino acid preprohormone in the preoptic anterior hypothalamus.
[7] The portal blood carries the GnRH to the pituitary gland, which contains the gonadotrope cells, where GnRH activates its own receptor, gonadotropin-releasing hormone receptor (GnRHR), a seven-transmembrane G-protein-coupled receptor that stimulates the beta isoform of Phosphoinositide phospholipase C, which goes on to mobilize calcium and protein kinase C. This results in the activation of proteins involved in the synthesis and secretion of the gonadotropins LH and FSH.
GnRH activity is elevating during fetal life, drops briefly following birth due to the effect of placental hormones, then becomes elevated again for the first one to six months of life in a period known as minipuberty, during which time gonadotropins and sex steroids contribute to the development of sexual organs.
Pulsatile activity can be disrupted by hypothalamic-pituitary disease, either dysfunction (i.e., hypothalamic suppression) or organic lesions (trauma, tumor).
Thus, a single hormone, GnRH1, controls a complex process of follicular growth, ovulation, and corpus luteum maintenance in the female, and spermatogenesis in the male.
GnRH neurons originate in the nose and migrate into the brain, where they are scattered throughout the medial septum and hypothalamus and connected by very long >1-millimeter-long dendrites.
[14] GnRH is found in organs outside of the hypothalamus and pituitary, and its role in other life processes is poorly understood.
[citation needed] Multiple neuronal regions in the limbic system send signals to the hypothalamus to modulate the amount of GnRH production and the frequency of pulses.
[23] In a similar concept, its use to deliver toxins to pituitary gonadotropes in animals has been explored as a means of sterilization, with limited success.
[27] GnRH agonists appear to be effective in protecting the ovaries during chemotherapy, in terms of menstruation recovery or maintenance, premature ovarian failure and ovulation.
GnRH injections enhance copulation solicitation (a type of courtship display) in white-crowned sparrows.
[28] In mammals, GnRH injections facilitate sexual behavior of female display behaviors as shown with the musk shrew's (Suncus murinus) reduced latency in displaying rump presents and tail wagging towards males.
[31] The natural hormone is also used in veterinary medicine as a treatment for cattle with cystic ovarian disease.