WBR0510
| Author | [[PageAuthor::Gonzalo A. Romero, M.D. [1] (Reviewed by Will Gibson)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology, MainCategory::Physiology |
| Sub Category | SubCategory::Endocrine, SubCategory::Reproductive |
| Prompt | [[Prompt::A pharmacist is planning a study with mice in order to determine the effects of a novel drug called “Compound A572”. He knows that the drug is supposed to work in the hypothalamus, to regulate the release of different pituitary hormones. He measures serum concentration of hypothalamic hormones and determines that the drug causes different changes in FSH and LH if dosed continuously or in a pulsatile fashion. Which of the following drugs has a similar mechanism of action as “Compound A572”?]] |
| Answer A | AnswerA::Flutamide |
| Answer A Explanation | [[AnswerAExp::Flutamide is a nonsteroidal competitive inhibitor of androgens at the androgen receptor. It is used to treat prostate cancer and hyperandrogenism in polycystic ovarian syndrome.]] |
| Answer B | AnswerB::Finasteride |
| Answer B Explanation | [[AnswerBExp::Finasteride is a 5 alpha-reductase inhibitor used to treat benign prostatic hyperplasia and male-pattern baldness.]] |
| Answer C | AnswerC::Mifepristone |
| Answer C Explanation | [[AnswerCExp::Mifepristone is a competitive inhibitor of progestins at the progesterone receptors. It is used to terminate pregnancy in combination with misoprostol (PGE1 analogue).]] |
| Answer D | AnswerD::Ketoconazole |
| Answer D Explanation | [[AnswerDExp::Ketoconazole is a steroid synthesis inhibitor that inhibits desmolase, the enzyme responsible for transforming cholesterol into pregnenolone.]] |
| Answer E | AnswerE::Leuprolide |
| Answer E Explanation | AnswerEExp::Leuprolide is a GnRH analogue |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::Leuprolide is a GnRH analogue. If used in pulsatile fashion, it acts as an agonist, while if used continuously, it acts as an antagonist. Continuous dosing of the drug causes the posterior pituitary to downregulate GnRH receptors due to negative feedback. The posterior pituitary thereby decreases the production of FSH and LH. Recall that FSH and LH are responsible for stimulating the release of sex hormones in both men and women. Leuprolide therefore has important therapeutic roles in diseases associated with the activity of sex hormones.
It is often used continuously with flutamide to treat prostatic cancer or uterine fibroids. Leuprolide is often used pulsatile in cases of infertility.
References: First Aid 2014 page 590]] |
| Approved | Approved::No |
| Keyword | WBRKeyword::Pituitary hormones, WBRKeyword::Pituitary |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |