Inhibin

protein
Name = inhibin, alpha
caption =


width =
HGNCid = 6065
Symbol = INHA
AltSymbols =
EntrezGene = 3623
OMIM = 147380
RefSeq = NM_002191
UniProt = P05111
PDB =
ECnumber =
Chromosome=2
Arm=q
Band=33-qter
LocusSupplementaryData = protein
Name = inhibin, beta A (activin A, activin AB alpha polypeptide)
caption =


width =
HGNCid = 6066
Symbol = INHBA
AltSymbols =
EntrezGene = 3624
OMIM = 147290
RefSeq = NM_002192
UniProt = P08476
PDB =
ECnumber =
Chromosome = 7
Arm = p
Band = 15
LocusSupplementaryData = -p13protein
Name = inhibin, beta B (activin AB beta polypeptide)
caption =


width =
HGNCid = 6067
Symbol = INHBB
AltSymbols =
EntrezGene = 3625
OMIM = 147390
RefSeq = NM_002193
UniProt = P09529
PDB =
ECnumber =
Chromosome = 2
Arm = cen
Band =
LocusSupplementaryData = -q13

Inhibin is a peptide that is an inhibitor of FSH synthesis and secretion, [cite journal |author=van Zonneveld P, Scheffer G, Broekmans F, Blankenstein M, de Jong F, Looman C, Habbema J, te Velde E |title=Do cycle disturbances explain the age-related decline of female fertility? Cycle characteristics of women aged over 40 years compared with a reference population of young women |journal=Hum Reprod |volume=18 |issue=3 |pages=495–501 |year=2003 |pmid=12615813 |doi=10.1093/humrep/deg138] and participates in the regulation of the menstrual cycle.

tructure

Inhibin contains an alpha and beta subunit linked by disulfide bonds. Two forms of inhibin differ in their beta subunits (A or B), while their alpha subunits are identical.

Inhibin belongs to the transforming growth factor-β (TGF-β) superfamily.

Action

In both females and males, inhibin inhibits FSH production. However, the overall mechanism differs between the genders:

In females

In women, FSH stimulates the secretion of inhibin from the granulosa cells of the ovarian follicles in ovary. In turn, inhibin suppresses FSH.

Inhibin secretion is diminished by GnRH, and enhanced by insulin-like growth factor-1 (IGF-1).

* "Inhibin B" reaches a peak in the early- to mid-follicular phase, and a second peak at ovulation.

* "Inhibin A" reaches its peak in the mid-luteal phase.

Inhibin is produced in the gonads, pituitary gland, placenta and other organs.

In males

In men, it is a hormone that inhibits FSH production leading to reduced testosterone secretion. It is secreted from the Sertoli cells, [cite journal |author=Skinner M, McLachlan R, Bremner W |title=Stimulation of Sertoli cell inhibin secretion by the testicular paracrine factor PModS |journal=Mol Cell Endocrinol |volume=66 |issue=2 |pages=239–49 |year=1989 |pmid=2515083 |doi=10.1016/0303-7207(89)90036-1] located in the seminiferous tubules inside the testes.

Activin

Activin is a related peptide that counteracts inhibin.

Clinical significance

Quantification of inhibin A is part of the prenatal quad screen that can be administered during pregnancy at a gestational age of 16-18 weeks. An elevated inhibin A (along with an increased beta-hCG, decreased AFP, and a decreased estriol) is [cite journal |author=Aitken D, Wallace E, Crossley J, Swanston I, van Pareren Y, van Maarle M, Groome N, Macri J, Connor J |title=Dimeric inhibin A as a marker for Down's syndrome in early pregnancy |journal=N Engl J Med |volume=334 |issue=19 |pages=1231–6 |year=1996 |pmid=8606718 | url = http://content.nejm.org/cgi/content/short/334/19/1231 |doi=10.1056/NEJM199605093341904 ] suggestive of the presence of a fetus with Down's syndrome. As a screening test, abnormal quad screen test results need to be followed up with more definitive tests.

It also has been used as a marker for ovarian cancer. [cite journal |author=Robertson D, Pruysers E, Jobling T |title=Inhibin as a diagnostic marker for ovarian cancer |journal=Cancer Lett |volume= |issue= |pages= |year= |pmid=17320281] [cite journal |author=Robertson D, Pruysers E, Burger H, Jobling T, McNeilage J, Healy D |title=Inhibins and ovarian cancer |journal=Mol Cell Endocrinol |volume=225 |issue=1-2 |pages=65–71 |year=2004 |pmid=15451569 |doi=10.1016/j.mce.2004.02.014]

References