A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 63-year-old man comes to the physician because of a 4-month history of urinary hesitancy and poor urinary stream. Digital rectal examination shows a symmetrically enlarged, nontender prostate. Serum studies show a prostate-specific antigen concentration of 2 ng/mL (N < 4). Pharmacotherapy with finasteride is initiated. Which of the following is the most likely effect of this drug?
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A
Decreased internal urethral sphincter toneIncorrect. Decreased internal urethral sphincter (bladder neck) tone describes ALPHA-1 BLOCKER action (tamsulosin), not finasteride.
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B
Increased prostatic apoptosisCorrect. Finasteride blocks 5-alpha reductase, lowering intraprostatic DHT and inducing PROSTATIC APOPTOSIS, gradually shrinking the gland.
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C
Increased penile blood flowIncorrect. Increased penile blood flow describes PDE-5 inhibitors (sildenafil); finasteride may actually decrease erectile function.
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D
Decreased bladder contractionsIncorrect. Decreased bladder contractions describes anticholinergics (e.g., oxybutynin) used for overactive bladder, not finasteride.
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E
Inhibition of dihydrotestosterone binding to the androgen receptorIncorrect. DHT-receptor blockade describes nonsteroidal anti-androgens (flutamide, bicalutamide) used in prostate cancer; finasteride acts upstream by blocking 5-alpha reductase, not by competing at the receptor.
↑ Tap an answer to reveal the reasoning
Answer: B. BPH symptoms (urinary hesitancy, weak stream) with a symmetrically enlarged, benign-feeling prostate and a normal PSA indicate BPH. Pharmacotherapy options for BPH include: (1) ALPHA-1 BLOCKERS (tamsulosin, alfuzosin, terazosin)—rapidly relax smooth muscle at the bladder neck/prostatic urethra (the 'dynamic' component); and (2) 5-ALPHA REDUCTASE INHIBITORS (finasteride, dutasteride)—shrink the prostate over 3-6 months by reducing intraprostatic dihydrotestosterone (the 'static' component).
Finasteride inhibits type II 5-alpha reductase, which converts testosterone to DHT in prostate (and hair follicles, skin). With markedly reduced DHT, prostate epithelium UNDERGOES APOPTOSIS, decreasing prostate volume by 20-30% over 6-12 months. The effect on urinary symptoms is gradual but durable, and finasteride is most effective in larger prostates (>40 mL). Finasteride also LOWERS PSA by ~50%, which must be accounted for in cancer screening (multiply by 2). Side effects include decreased libido, erectile dysfunction, gynecomastia, and decreased ejaculate volume—all reflecting reduced androgen action.
Finasteride is also used at lower doses for male-pattern baldness (Propecia 1 mg).
**Why each option:**
**A.** Decreased internal urethral sphincter (bladder neck) tone describes ALPHA-1 BLOCKER action (tamsulosin), not finasteride.
**B.** Correct. Finasteride blocks 5-alpha reductase, lowering intraprostatic DHT and inducing PROSTATIC APOPTOSIS, gradually shrinking the gland.
**C.** Increased penile blood flow describes PDE-5 inhibitors (sildenafil); finasteride may actually decrease erectile function.
**D.** Decreased bladder contractions describes anticholinergics (e.g., oxybutynin) used for overactive bladder, not finasteride.