Inhibin

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inhibin, alpha
Identifiers
Symbol	INHA
HUGO	6065
Entrez	3623
OMIM	147380
RefSeq	NM_002191
UniProt	P05111
Other data
Locus	Chr. 2 q33-qter

inhibin, beta A (activin A, activin AB alpha polypeptide)
Identifiers
Symbol	INHBA
HUGO	6066
Entrez	3624
OMIM	147290
RefSeq	NM_002192
UniProt	P08476
Other data
Locus	Chr. 7 p15-p13

inhibin, beta B (activin AB beta polypeptide)
Identifiers
Symbol	INHBB
HUGO	6067
Entrez	3625
OMIM	147390
RefSeq	NM_002193
UniProt	P09529
Other data
Locus	Chr. 2 cen-q13

Inhibin is a peptide that is an inhibitor of FSH synthesis and secretion,^[1] and participates in the regulation of the menstrual cycle.

1 Structure
2 Action
- 2.1 In women
- 2.2 In men
3 Activin
4 Clinical significance
5 References

[edit] Structure

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.

[edit] Action

[edit] In women

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.

[edit] In men

In men, it is a hormone that inhibits FSH production.

It is secreted from the Sertoli cells,^[2] located in the seminiferous tubule inside the testes.

[edit] Activin

Activin is a related peptide that counteracts inhibin.

[edit] 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 ^[3] suggestive of the presence of a fetus with Downs 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.^[4]^[5]

[edit] References

^ van Zonneveld P, Scheffer G, Broekmans F, Blankenstein M, de Jong F, Looman C, Habbema J, te Velde E (2003). "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". Hum Reprod 18 (3): 495-501. PMID 12615813.
^ Skinner M, McLachlan R, Bremner W (1989). "Stimulation of Sertoli cell inhibin secretion by the testicular paracrine factor PModS". Mol Cell Endocrinol 66 (2): 239-49. PMID 2515083.
^ Aitken D, Wallace E, Crossley J, Swanston I, van Pareren Y, van Maarle M, Groome N, Macri J, Connor J (1996). "Dimeric inhibin A as a marker for Down's syndrome in early pregnancy". N Engl J Med 334 (19): 1231-6. PMID 8606718.
^ Robertson D, Pruysers E, Jobling T. "Inhibin as a diagnostic marker for ovarian cancer". Cancer Lett. PMID 17320281.
^ Robertson D, Pruysers E, Burger H, Jobling T, McNeilage J, Healy D (2004). "Inhibins and ovarian cancer". Mol Cell Endocrinol 225 (1-2): 65-71. PMID 15451569.