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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.
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.
Activin is a related peptide that counteracts inhibin.
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  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.
- ↑ , David A. Aitken, Ph.D., Euan M. Wallace, M.R.C.O.G., Jennifer A. Crossley, Ph.D., Ian A. Swanston, B.Sc., Yvonne van Pareren, M.Sc., Merel van Maarle, M.Sc., Nigel P. Groome, Ph.D., James N. Macri, Ph.D., and J. Michael Connor, M.D. (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.
|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
Cell signaling: TGF beta signaling pathway
|TGF beta superfamily of ligands||
TGF beta family (TGF-β1, TGF-β2, TGF-β3)
|TGF beta receptors|
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