So is Inhibin
Inhibin is a glycoprotein hormone belonging to the superfamily of transforming ß growth factors (TGF-ß), which also includes activin. Two forms are known: inhibin A and inhibin B, both consisting of two alpha and beta subunits (respectively α - ΒA and α - ΒB).
Functions
The main biological role of inhibin is to selectively suppress the secretion of the follicle stimulating pituitary hormone or FSH. This hormone, also known as FSH, promotes spermatogenesis in men, ie the synthesis of new spermatozoa, while in women it induces the maturation of ovarian follicles.
Inhibin is mainly secreted by the granulosa cells of the ovary in the woman and by the testicular cells of the Sertoli in the man. Its inhibitory action on the secretion of FSH occurs through the inhibition of activin, which instead carries out a stimulus activity. .
Inhibin decreases the biosynthesis and release of FSH, while activin increases them.
Clinical significance
The dosage of inhibin A is part of the so-called quadruple-test, a screening test carried out around the 16th-18th week of pregnancy to identify pregnant women with the highest risk of carrying fetuses with Down syndrome. This risk is considered high when the mother has high blood levels of inhibin A and human chorionic gonadotropin, associated with a reduction in those of estriol and alpha-fetoprotein. Being a screening test, high-risk pregnant women are directed to more specific diagnostic tests and examinations, such as " amniocentesis.
The dosage of inhibin B in men can be used as a marker of spermatogenesis and male fertility. In particular, very low levels of inhibin B indicate insufficient or no production of spermatozoa and advise against taking them from the testicle with the TESE method. More generally, the average inhibin B levels in fertile men are higher than in individuals with infertility problems.
Still in the context of assisted fertilization methods, inhibin B can be used, in the same way as estradiol, to control follicular growth (control of superovulation cycles). The dosage of inhibin B also allows an assessment of the reserve ovarian and ovulation induction prediction.
The measurement of inhibin blood levels has also been proposed as tumor markers of ovarian cancer, in particular of the forms affecting granulosa cells.
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