For millions of men worldwide, an enlarged prostate, a condition known as benign prostatic hyperplasia (BPH), can lead to bothersome urinary symptoms such as frequent urination, weak stream, and difficulty emptying the bladder. The search for a remedy often leads to medications like finasteride, which many patients hope will reverse the growth of the prostate gland itself.
The Role of Dihydrotestosterone (DHT) in Prostate Growth
To understand how finasteride works, it's essential to know the role of the androgen hormone dihydrotestosterone (DHT) in prostate health. The prostate gland's growth is heavily dependent on androgens. Specifically, DHT, a potent form of testosterone, acts as the primary hormone responsible for prostate tissue proliferation and enlargement.
DHT is synthesized from testosterone by an enzyme called 5-alpha reductase (5α-reductase). By inhibiting this enzyme, finasteride prevents the conversion of testosterone into DHT, thereby lowering the levels of DHT in both the bloodstream and the prostate tissue. Reduced DHT levels subsequently lead to the shrinkage of the prostate gland over time.
How Finasteride Shrinks the Prostate
Finasteride is classified as a 5α-reductase inhibitor. A specific strength of finasteride (marketed under the brand name Proscar) is used for treating BPH. The mechanism is a targeted attack on the root cause of prostate overgrowth. By blocking the action of the Type 2 5α-reductase isoenzyme, finasteride significantly reduces intraprostatic DHT levels.
- Reduction in Prostate Volume: Clinical studies provide substantial evidence of finasteride's ability to shrink the prostate. A landmark 12-month study, for instance, reported that men treated with finasteride experienced a significant decrease in prostatic volume, compared to only a minimal change in the placebo group. Another meta-analysis found that finasteride is most effective in men with large prostates, with those having a baseline prostate volume over 40 cc showing the most significant volume reduction.
- Symptom Improvement: The decrease in prostate size directly corresponds to an improvement in urinary symptoms. By reducing the volume of the prostate, finasteride can alleviate the pressure on the urethra, leading to a stronger urine stream and a decrease in urinary frequency and urgency.
- Long-Term Effects: The effects of finasteride are not temporary. Long-term studies, some extending over six years, have confirmed that the benefits of finasteride in reducing prostate volume and improving symptoms are sustained with continued use. When treatment is discontinued, the prostate begins to grow again.
Finasteride vs. Other BPH Medications
Finasteride belongs to a class of drugs known as 5α-reductase inhibitors. A related medication, dutasteride (Avodart), works similarly but inhibits both Type 1 and Type 2 5α-reductase. It's useful to compare their effects.
| Feature | Finasteride (Proscar) | Dutasteride (Avodart) |
|---|---|---|
| Mechanism | Inhibits Type 2 5α-reductase | Inhibits both Type 1 and 2 5α-reductase |
| DHT Inhibition | Significant reduction in serum DHT | More complete reduction in serum DHT |
| Prostate Shrinkage | Clinical trials show significant reduction over 1 year | Clinical trials show significant reduction over 1-2 years |
| Onset of Action | Faster onset of symptom relief | Slower onset but potentially greater long-term shrinkage |
| Half-Life | Relatively shorter | Relatively longer |
| Combination Therapy | Often combined with alpha-blockers like doxazosin | Can also be combined with alpha-blockers |
Potential Side Effects of Finasteride
While effective, finasteride is not without potential side effects, which may differ depending on the strength used. Most side effects are related to the drug's hormonal action.
Common Side Effects (may be more likely with certain strengths):
- Sexual Dysfunction: Decreased libido, erectile dysfunction, and problems with ejaculation are commonly reported.
- Breast Changes: Breast enlargement (gynecomastia) and tenderness can occur, though less frequently.
- Other: Dizziness and low blood pressure (especially with alpha-blocker combination) are also possible.
Less Common but Serious Side Effects:
- Post-Finasteride Syndrome (PFS): Some men report persistent sexual and mental side effects (e.g., depression, anxiety) even after stopping the medication. This is a rare but serious concern.
- Prostate Cancer Risk: The Prostate Cancer Prevention Trial (PCPT) found a reduced risk of overall prostate cancer but a small, statistically significant increase in the risk of high-grade prostate cancer in the finasteride group. The potential reasons for this observation are complex and debated, but it's a risk to discuss with a doctor.
Conclusion
So, does finasteride really shrink the prostate? The answer is a clear yes, based on decades of clinical research. By inhibiting the conversion of testosterone to DHT, finasteride directly addresses the hormonal driver of BPH. For men with moderate to large prostates, this leads to a measurable and sustained reduction in prostate size, resulting in significant symptom improvement and reduced risk of complications like acute urinary retention.
However, this medication is not without trade-offs. The potential for sexual side effects and other risks necessitates a careful discussion with a healthcare provider. The decision to begin finasteride should be made in consultation with a doctor, who can weigh the benefits of symptom relief and prostate shrinkage against the potential adverse effects based on an individual's health profile.
