Benign prostatic hyperplasia (BPH) is a common condition among older men, affecting approximately 50% of men over age 50 and 80% of those over age 80, often leading to uncomfortable urinary symptoms. Various factors are proposed in BPH’s pathophysiology, with emerging evidence suggesting that insulin and insulin resistance could be independent risk factors. This study investigates whether insulin resistance is linked to baseline prostate volume (PV) and PV growth over a four-year period within the REDUCE trial. The analysis included 2,804 men on placebo and 2,712 men on dutasteride, a drug aimed at reducing prostate cancer risk. Participants, all aged between 50 and 75 with elevated PSA levels but negative biopsies before the study, underwent transrectal ultrasound to measure PV at baseline and at 2- and 4-year follow-ups.
The study used the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) to quantify insulin resistance, categorizing subjects into placebo and dutasteride groups and correlating HOMA-IR scores with PV at different intervals. Findings from Pearson correlation analysis indicated a significant, though modest, association between higher HOMA-IR and increased baseline PV in both groups. Specifically, in the placebo group, the median PV was 40.4 ml in the lowest HOMA-IR quartile, compared to 46.3 ml in the highest quartile (p=0.02). In the dutasteride group, results were similar, with a median PV of 42.2 ml in the lowest HOMA-IR quartile versus 45.9 ml in the highest (p=0.007). Despite this association at baseline, HOMA-IR was not related to changes in PV over the study duration for either group.
Thus, while higher insulin resistance appears to be weakly correlated with larger initial prostate volume, it does not impact prostate growth significantly over time. These findings suggest a possible biological connection between insulin resistance and prostate size, though the link may not hold significant clinical importance.
