The question asks us to identify which substance is a glucocorticoid synthesis inhibitor from the given options. Let's analyze each of these:
- Mifepristone: This drug is primarily an antagonist of the progesterone receptor and also acts as an antagonist of the glucocorticoid receptor, but it does not inhibit glucocorticoid synthesis.
- Flutamide: This is an anti-androgen used in the treatment of prostate cancer, functioning as an androgen receptor blocker, not related to glucocorticoid synthesis.
- Finasteride: This drug is a 5-alpha-reductase inhibitor used in the treatment of benign prostatic hyperplasia and male pattern baldness by preventing the conversion of testosterone to dihydrotestosterone (DHT). It has no effect on glucocorticoid synthesis.
- Metyrapone: Metyrapone inhibits the enzyme 11-beta-hydroxylase, which is crucial in the biosynthesis of cortisol, a glucocorticoid. Therefore, it effectively serves as a glucocorticoid synthesis inhibitor by blocking this pathway.
Given this analysis, the correct choice for a glucocorticoid synthesis inhibitor is Metyrapone.
