Everything about Gonadotropins totally explained
Gonadotropins are
protein hormones secreted by
gonadotrope cells of the
pituitary gland of
vertebrates.
Gonadotropin is sometimes abbreviated
Gn. The British spelling is
gonadotrophin.
Types
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 interactions.
A third human gonadotropin is
human chorionic gonadotropin (hCG), produced by the
placenta during
pregnancy.
Mechanism
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.
Diseases
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 by 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, since the pituitary gland tries to compensate for the insufficient gonads.
Further Information
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