This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Osteoporosis, Sex Hormones and OCPs, Subject name: Pharmacology
An old man is having benign prostatic hyperophy. Which of the following drug is used to reduce the size of prostate in such a person? 
Select and explain. 
A. Cyproterone acetate, B. Danazol, C. Bicalutamide, D. Finasteride
D: Finasteride
Answer: D: Finasteride 
Explanation: DRUGS FOR BHP Alpha blockers like tamsulosin, prazosin etc relax the prostatic urethra and provide symptomatic relief from BHP. These relieve the dynamic component of obstruction and are very fast acting. Finasteride and dutasteride are 5-a reductase inhibitors useful in the treatment of BHP. These decrease the size of prostate (static component). However, these are very slow acting.