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Alpha inhibin Symbol(s): INHA Genetic data Locus: Chr. 2 q33-qter Database Links Entrez: 3623 OMIM: 147380 RefSeq: NM_002191 UniProt: P05111

inhibin, beta A Symbol(s): INHBA Genetic data Locus: Chr. 7 p15-p13 Database Links Entrez: 3624 OMIM: 147290 RefSeq: NM_002192 UniProt: P08476

inhibin, beta B Symbol(s): INHBB Genetic data Locus: Chr. 2 cen-q13 Database Links Entrez: 3625 OMIM: 147390 RefSeq: NM_002193 UniProt: P09529

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

Contents 1 Structure 2 Action 3 Activin 4 Prenatal Testing 5 External links 6 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) family.

[edit] Action

In women, FSH stimulates the secretion of inhibin from the granulosa cells of the 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, in contrast to inhibin A, which reaches its peak in the mid-luteal phase. Inhibin is produced in the gonads, pituitary gland, placenta and other organs.

In men, it is a hormone that inhibits FSH production. It is secreted from the sustentacular cell, located in the seminiferous tubule inside the testes.

[edit] Activin

Activin is a related peptide that counteracts inhibin.

[edit] Prenatal Testing

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 <ref> (1996-05-09) "Dimeric Inhibin A as a Marker for Down's Syndrome in Early Pregnancy". New England Journal of Medicine, The 334 (19): 1231-1236. Retrieved on 2006-08-04.</ref> 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.

[edit] External links

• http://www.inhibin.com

[edit] References

<references/>

Hormones and endocrine glands - edit

Hypothalamus: - TRH - CRH - GnRH - GHRH - somatostatin - dopamine | Posterior pituitary: vasopressin - oxytocin - lipotropin | Anterior pituitary: GH - ACTH - TSH - LH - FSH - prolactin - MSH - endorphins - lipotropin Thyroid: T3 and T4 - calcitonin | Parathyroid: PTH | Adrenal medulla: epinephrine - norepinephrine | Adrenal cortex: aldosterone - cortisol - DHEA | Pancreas: glucagon- insulin - somatostatin | Ovary: estradiol - progesterone - inhibin - activin | Testis: testosterone - AMH - inhibin | Pineal gland: melatonin | Kidney: renin - EPO - calcitriol - prostaglandin | Heart atrium: ANP Stomach: gastrin | Duodenum: CCK - GIP - secretin - motilin - VIP | Ileum: enteroglucagon | Liver: IGF-1 Placenta: hCG - HPL - estrogen - progesterone Adipose tissue: leptin, adiponectin Target-derived NGF, BDNF, NT-3

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