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What is the significance of G protein-coupled signaling and desensitization in the mechanism of action of gonadotropins?
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Correct answer:
The G protein-coupled cAMP pathway is the principal mediator of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) receptor activity. Receptors for FSH and LH are located in the plasma membranes of ovarian granulosa cells and testicular Sertoli cells. When FSH and LH interact with their respective receptors this leads to conformational changes in the receptor. These changes then activate the G protein-coupled signaling system. In addition, binding of FSH and LH also leads to desensitization that reduces the gonadal cell's responsiveness to ongoing stimulation. This concept is applied clinically in the use of both gonadotropin-releasing hormone (GnRH) agonists and antagonists, as prolonged exposure (agonist) or competitive inhibition (antagonist) will suppress secretion of FSH and LH.
