London, UK—Medications to treat enlarged prostate symptoms might also increase men’s risk of developing type 2 diabetes, according to a new study.

The report in the British Health Journal doesn’t suggest discontinuing the drugs but advises that users might need additional health screenings.

University College London–led researchers point out that men with enlarged prostates are commonly prescribed drugs called 5-alpha-reductase inhibitors, which help treat symptoms such as reduced urinary flow. They cite previous short-term studies suggesting that the medication, including finasteride and dutasteride, might affect metabolism and could reduce the body's response to insulin, an early sign of type 2 diabetes.

In response, the study team sought to investigate the incidence of new-onset type 2 diabetes mellitus in men receiving steroid 5-alpha-reductase inhibitors—dutasteride or finasteride—for long-term treatment of benign prostatic hyperplasia.

For the population-based cohort study, researchers used the UK Clinical Practice Research Datalink (CPRD; 2003-2014) and Taiwanese National Health Insurance Research Database (NHIRD; 2002-2012).

After propensity score matching reduced the cohorts to 1,251 using dutasteride, 2,445 using finasteride and 2,502 using tamsulosin, the study team found that, in the CPRD, 2,081 new-onset type 2 diabetes events (368 dutasteride, 1,207 finasteride, and 506 tamsulosin) were recorded during a mean follow-up time of 5.2 years. That translated to an event rate per 10,000 person years of 76.2 (95% CI, 68.4-84.0) for dutasteride, 76.6 (72.3-80.9) for finasteride, and 60.3 (55.1-65.5) for tamsulosin.

“There was a modest increased risk of type 2 diabetes for dutasteride (adjusted hazard ratio 1.32, 95% CI, 1.08-1.61) and finasteride (1.26, 1.10-1.45) compared with tamsulosin,” study authors explain, noting that results for the NHIRD were consistent with the findings for the CPRD—adjusted hazard ratio 1.34, 95% CI, 1.17 to 1.54 for dutasteride, and 1.49, 1.38-1.61 for finasteride compared with tamsulosin.

“The risk of developing new onset type 2 diabetes appears to be higher in men with benign prostatic hyperplasia exposed to 5-alpha-reductase inhibitors than in men receiving tamsulosin, but did not differ between men receiving dutasteride and those receiving finasteride,” study authors conclude. “Additional monitoring might be required for men starting these drugs, particularly in those with other risk factors for type 2 diabetes.”

“These findings will be particularly important for health screening in older men who are already typically at a higher risk of type 2 diabetes. We will now continue our studies to better understand the long-term outcomes so we can better identify patients at greater risk,” adds senior author Ruth Andrew, PhD, of the of the University/British Heart Foundation Centre for Cardiovascular Science at the University of Edinburgh.

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