Clinical Utility of Inhibin B in Men.

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-Definition:

Inhibin is a glycoprotein secreted by granulosa cells (female) and Sértoli cells (male) in response to Follicle Stimulating Hormone (FSH), and its major action is to control the secretion of FSH by negative feedback. There are 2 types of molecules, A and B depending on the subunit that composes them.
Inhibin B is increasing in women, from the late luteal phase and through the follicular phase accompanying FSH. FSH would cause an increase in Inhibin B by increasing the number of granulosa cells and follicles. It has been suggested that this is the product of developing follicles recruited in the anterior luteal phase
The regulation of gonadotropin secretion in males involves a complicated balance between stimulation by Gonadotropin-releasing hormone (GnRH) and negative feedback of testosterone from Leydig cells.
There would also be a nonsteroidal regulation mediated by Inhibin B, added to the modulation within the pituitary gland by Activin and Folistatin. FSH is necessary for the development of normal spermatogenesis, and the plasma levels of Inhibin A in the male are not detectable. The greatest diagnostic utility currently is based mainly on Inhibin B.
In women, the levels of Inhibin B are relatively constant or increase up to 40 years and then decrease with age. As it is produced by developing follicles, later measures in the follicular phase may reflect the size and quality of follicles.

-Importance:

In the male, Inhibin B is a first-order marker of the competence of the Sértoli cells and spermatogenesis. Thus, their levels are significantly lower in patients with defects in spermatogenesis, and normal in patients with an azoospermia whose only cause is an obstruction.
What is the same, Inhibin B reflects the function of the total testicular tissue, unlike a biopsy, which may not be representative. Its determination predicts the presence of a small amount of sperm in the testes, avoiding surgical intervention in cases of azoospermia and it¨s possible a testicular sperm extraction.

-Conclusions:

For a long time, the best parameter has been the level of FSH, since the high values correlate with a certain probability of sperm absence, but the values of inhibin B, provide us with more information about an undamaged testicle, if its values are low .
There is an inverse correlation between the levels of INHB and those of FSH and LH. INHB correlates better than FSH with sperm concentration. In azoospermias and oligospermias (<2M / ml) a decrease in inhibin B (INHB) is more sensitive to detect testicular damage than an increase in FSH.
The INHB predicts better than FSH sperm retrieval for intracytoplasmic sperm injection, (ICSI) which is an assisted reproduction technique included in IVF treatment that has allowed successful pregnancy in couples diagnosed with a severe male factor .
The male should provide a sample of semen or a testicular biopsy-if necessary-to extract and select the best sperm that will be used for the fertilization of the oocytes.
TESE is an acronym that in English means Testicular Sperm Extraction. It is actually a testicular biopsy that is only performed for the recovery of testicular sperm to be used in the IVF cycle.
The denomination TESE is used to differentiate it from the diagnostic biopsy. To increase the chances of finding sperm it may be necessary to extract several samples of testicular tissue, with local anesthesia.

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