Can finasteride reduce prostate size in hyperandrogenism?

From the Guidelines

Finasteride can effectively reduce prostate size in men with hyperandrogenism by inhibiting the conversion of testosterone to dihydrotestosterone (DHT), regardless of circulating testosterone levels. According to the most recent and highest quality study 1, finasteride, a 5-alpha-reductase inhibitor (5-ARI), can reduce the size of the prostate by 15-25% at six months, with a significant decrease in androgenic growth and an increase in apoptosis and atrophy. This leads to a reduction in prostate volume and an improvement in urinary symptoms. The study also notes that finasteride can reduce serum PSA levels by approximately 50%, which is an important consideration when screening men for prostate cancer who are on 5-ARIs.

The mechanism of action of finasteride involves the inhibition of the 5-AR type II isoenzyme, which reduces serum levels of DHT by approximately 70% 1. This reduction in DHT levels leads to a decrease in prostate growth and an improvement in urinary symptoms. The study also notes that finasteride has a slow onset of action compared to alpha blockers, and patients should be counseled on a slower symptom improvement if treated with 5-ARI alone.

Key points to consider when prescribing finasteride for hyperandrogenism include:

• Finasteride can reduce prostate size and improve urinary symptoms in men with BPH, regardless of circulating testosterone levels
• The drug specifically targets the prostate tissue's response to androgens, making it an effective treatment for BPH
• Finasteride can cause side effects such as decreased libido or erectile dysfunction in some men, and regular follow-ups with a healthcare provider are necessary to monitor progress and any potential side effects
• The reduction in serum PSA levels should be taken into account when screening men for prostate cancer who are on 5-ARIs, and the measured serum PSA value should be doubled to accurately gauge disease progression after 1 year of 5-ARI therapy 1.

From the FDA Drug Label

In A Long-Term Efficacy and Safety Study, prostate volume was assessed yearly by magnetic resonance imaging (MRI) in a subset of patients. In patients treated with finasteride tablets who remained on therapy, prostate volume was reduced compared with both baseline and placebo throughout the 4-year study. Finasteride tablets decreased prostate volume by 17.9% (from 55.9 cc at baseline to 45.8 cc at 4 years) compared with an increase of 14.1% (from 51.3 cc to 58.5 cc) in the placebo group (p<0.001).

Finasteride can reduce prostate size. The reduction in prostate volume was seen during the first year and maintained throughout an additional five years of open extension studies 2. However, the question is about hyperandrogenism, and the provided information is about BPH symptoms. Since the label does not directly address the effect of finasteride on prostate size in hyperandrogenism, no conclusion can be drawn for this specific condition.

From the Research

Finasteride and Prostate Size Reduction

• Finasteride has been shown to reduce prostate size in patients with benign prostatic hyperplasia (BPH) by blocking the conversion of testosterone to 5 alpha-dihydrotestosterone (5 alpha-DHT) 3, 4, 5, 6, 7.
• The mean reduction in prostate size was 20-25% after 6 months of therapy, and this effect was maintained as long as the patient was on the drug, at least up to the end of a 6-year follow-up period 5.
• Finasteride was also shown to reduce prostate volume by 22% after 6 months of therapy in a study of over 1600 patients 3.
• The reduction in prostate size was associated with improvements in peak urinary flow rate and urological symptoms, although the magnitude of clinical improvement was perceived to be modest 4.

Mechanism of Action

• Finasteride acts by inhibiting the enzyme 5 alpha-reductase, which is responsible for the conversion of testosterone to 5 alpha-DHT 3, 4, 5, 6, 7.
• The reduction in 5 alpha-DHT levels leads to a decrease in prostatic growth and a reduction in prostate size 5.

Clinical Studies

• Large phase III trials have demonstrated the efficacy of finasteride in treating BPH, with significant improvements in prostate size, peak urinary flow rate, and urological symptoms 3, 4, 5, 6.
• A study of 67 men with BPH found that treatment with finasteride for 12 months resulted in a significant reduction in prostate volume and an improvement in maximum urinary flow rate 7.
• Another study found that finasteride was well-tolerated, with most adverse events related to sexual dysfunction, and that the benefits of therapy appeared to outweigh the risks 4.