NAPLEX (North American Pharmacist Licensure Examination) Practice Exam

What do GnRH antagonists directly block to cause a rapid decrease in testosterone production?

1. Androgen receptors

2. GnRH receptors

3. Testosterone synthesis

4. Estrogen receptors

The correct answer is: GnRH receptors

GnRH antagonists directly block GnRH receptors to cause a rapid decrease in testosterone production. GnRH (gonadotropin-releasing hormone) receptors are located in the pituitary gland and are responsible for stimulating the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which in turn stimulate the production of testosterone in the testes. By blocking GnRH receptors, GnRH antagonists inhibit the release of LH and FSH, leading to decreased testosterone production. Option A (Androgen receptors) is incorrect because androgen receptors are proteins located inside cells that bind to testosterone and signal the cell to exhibit specific responses. GnRH antagonists do not directly interact with androgen receptors. Option C (Testosterone synthesis) is incorrect because GnRH antagonists do not directly block the process of testosterone synthesis within the testes. Instead, they act upstream in the hormone regulation pathway by blocking GnRH receptors. Option D (Estrogen receptors) is incorrect because GnRH antagonists primarily target GnRH receptors and do not have a direct effect on estrogen receptors or estrogen production.