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|MainCategory=Pharmacology
|MainCategory=Pharmacology
|SubCategory=Reproductive
|SubCategory=Reproductive
|Prompt=A 61-year-old male comes to the clinic due to hair loss.  He has a progressive history of baldness. He has tried many topical ointments and different products seen on TV, which have not been very helpful.  He would like to look younger and to prevent losing further hair.  The family doctor considers using Finasteride to treat his condition. Which of the following is true about the mechanism of action of this drug?
|Prompt=A 31-year-old man presents to the dermatology clinic for hair loss.  The patient reports progressive hairline regression and hair loss mainly localized above the temples and at the vertex.  He also explains that he has a strong family history of androgenic alopecia, and cannot stand the idea of going completely bald. The patient has tried many topical products intended for hair loss, which have not been very helpful.  You consider using an agent that is also approved for the treatment of benign prostatic hyperplasia. Which of the following is the most likely mechanism of action of this drug?
|Explanation=Finasteride is used for [[BPH]] (benigh prostatic hyperplasia) and to treat male-pattern baldness,because it promotes hair growth. It is an 5 alfa-reductase inhibitor (normally converts [[testosterone]] to [[DHT]]), decreasing the conversion of testosterone to DHT (dihydrotestosterone).
|Explanation=Finasteride is used for [[BPH]] (benigh prostatic hyperplasia) and to treat male-pattern baldness,because it promotes hair growth. It is an 5 alfa-reductase inhibitor (normally converts [[testosterone]] to [[DHT]]), decreasing the conversion of testosterone to DHT (dihydrotestosterone).
|AnswerA=It is a non-steroidal competitive inhibitor of androgens at the testosterone receptor
|AnswerA=Phosphodiesterase 5 (PDE5) inhibitor
|AnswerAExp=This refers to the mechanism of action of [[flutamide]] which is used in [[prostatic carcinoma]].
|AnswerAExp=Sildenafil, tadalafil - erectile dysfunction
|AnswerB=Inhibits the synthesis of steroid
|AnswerB=Competitive inhibitor of testosterone binding at androgen receptors
|AnswerBExp=[[Ketoconazole]] inhibits steroid synthesis by inhibiting desmolase (normally converts cholesterol to [[pregnenolone]]). ACTH stimulates the activity of desmolase.
|AnswerBExp=flutamide - Nonsteroidal antiandrogen - Prostate Cancer
|AnswerC=Inhibits the conversion of testosterone to DHT
|AnswerC=Aromatase inhibitor
|AnswerCExp=It is incorrect because
|AnswerCExp=exemestane - Breast Cancer
|AnswerD=Inhibits steroid binding
|AnswerD=Agonist of luteinizing hormone-releasing hormone (LHRH)
|AnswerDExp=[[ Spironolactone]] inhibits the androgen binding to its receptors.  It is a potasium sparing diuretic. [[Flutamide]] and cyproterone also inhibit the androgen-receptor interaction.
|AnswerDExp=leuprolide - Prostate Cancer - Endometriosis - Leiomyoma
|AnswerE=Binds to estrogen receptors
|AnswerE=Selective inhibitior of 5-alpha-reductase
|AnswerEExp=[[Estrogens]] such as ethinyl estradiol, DES, mestranol bind to estrogen receptors, acting as agonists. Estrogen receptor antagonists include [[tamoxifen]], [[raloxifene]] and [[fulvestrant]].
|AnswerEExp=finasteride
|EducationalObjectives=Finasteride inhibits the conversion of testosterone to DHT, and can be used to treat prostatic hyperplasia and male pattern baldness.
|References=First Aid 2014 page 589
|References=First Aid 2014 page 589
|RightAnswer=C
|RightAnswer=E
|WBRKeyword=Testosterone agonist, testosterone antagonist
|WBRKeyword=Testosterone agonist, testosterone antagonist
|Approved=No
|Approved=No
}}
}}

Revision as of 14:01, 16 September 2014
Author [[PageAuthor::Gonzalo A. Romero, M.D. [1]]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Pharmacology
Sub Category SubCategory::Reproductive
Prompt [[Prompt::A 31-year-old man presents to the dermatology clinic for hair loss. The patient reports progressive hairline regression and hair loss mainly localized above the temples and at the vertex. He also explains that he has a strong family history of androgenic alopecia, and cannot stand the idea of going completely bald. The patient has tried many topical products intended for hair loss, which have not been very helpful. You consider using an agent that is also approved for the treatment of benign prostatic hyperplasia. Which of the following is the most likely mechanism of action of this drug?]]
Answer A AnswerA::Phosphodiesterase 5 (PDE5) inhibitor
Answer A Explanation AnswerAExp::Sildenafil, tadalafil - erectile dysfunction
Answer B AnswerB::Competitive inhibitor of testosterone binding at androgen receptors
Answer B Explanation AnswerBExp::flutamide - Nonsteroidal antiandrogen - Prostate Cancer
Answer C AnswerC::Aromatase inhibitor
Answer C Explanation AnswerCExp::exemestane - Breast Cancer
Answer D AnswerD::Agonist of luteinizing hormone-releasing hormone (LHRH)
Answer D Explanation AnswerDExp::leuprolide - Prostate Cancer - Endometriosis - Leiomyoma
Answer E AnswerE::Selective inhibitior of 5-alpha-reductase
Answer E Explanation AnswerEExp::finasteride
Right Answer RightAnswer::E
Explanation [[Explanation::Finasteride is used for BPH (benigh prostatic hyperplasia) and to treat male-pattern baldness,because it promotes hair growth. It is an 5 alfa-reductase inhibitor (normally converts testosterone to DHT), decreasing the conversion of testosterone to DHT (dihydrotestosterone).

Educational Objective:
References: First Aid 2014 page 589]]

Approved Approved::No
Keyword WBRKeyword::Testosterone agonist, WBRKeyword::testosterone antagonist
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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