are protein hormones
secreted by gonadotrope cells
of the pituitary gland
Gonadotropin is sometimes abbreviated Gn. The British spelling is gonadotrophin.
The two principal gonadotropins are luteinizing hormone
(LH) and follicle stimulating hormone
(FSH). Both hormones consist of two peptide
chains, an alpha chain and a beta chain, linked by Hydrogen bonds
and van der Waals
forces. LH and FSH share nearly identical alpha chains, while the beta chain provides specificity for receptor
A third human gonadotropin is human chorionic gonadotropin (hCG), produced by the placenta during pregnancy.
Gonadotropin receptors are embedded in the surface of the target cell membranes
and coupled to the G-protein
system. Signals triggered by binding to the receptor are relayed within the cells by the cyclic AMP
second messenger system.
Gonadotropins are released under the control of gonadotropin-releasing hormone (GnRH) from the arcuate nucleus and preoptic area of the hypothalamus. The gonads — testes and ovaries — are the primary target organs for LH and FSH. The gonadotropins affect multiple cell types and elicit multiple responses from the target organs. As a simplified generalization, LH stimulates the Leydig cells of the testes and the theca cells of the ovaries to produce testosterone (and indirectly estradiol), while FSH stimulates the spermatogenic tissue of the testes and the granulosa cells of ovarian follicles.
Gonadotropin deficiency due to pituitary
disease results in hypogonadism
, which can lead to infertility
. Treatment include administered gonadotropins, which therefore work as fertility medication
. Such can either be produced by extraction and purification from urine or it can be produced by recombinant DNA
Failure or loss of the gonads usually results in elevated levels of LH and FSH in the blood.