The risk of myocardial infarction (MI) is increased following initiation of testosterone therapy (TT) in men, according to research published in PLOS ONE.

William D. Finkle, Ph.D., of Consolidated Research in Los Angeles, and colleagues conducted a cohort study involving 55,593 men who filled a first prescription for TT to assess the association between TT and risk of myocardial infarction.

The researchers found that the post-prescription/pre-prescription rate ratio (RR) for risk of acute nonfatal MI in the 90 days following an initial TT prescription was 1.36 (95 percent confidence interval [CI], 1.03 to 1.81). For men aged 65 years and older, the RR was 2.19 (95 percent CI, 1.27 to 3.77) for TT prescription and 1.15 (95 percent CI, 0.83 to 1.59) for phosphodiesterase type 5 inhibitor (PDE5I) prescription.

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The RR for TT prescription increased with age, from 0.95 (95 percent CI, 0.54 to 1.67) for men under age 55 years to 3.43 (95 percent CI, 1.54 to 7.56) for those aged 75 years and older (Ptrend = 0.03); no trend was seen for PDE5I (Ptrend = 0.18). For men younger than 65 years, TT prescription was associated with increased risk of MI for those with a history of heart disease (RR, 2.90; 95 percent CI, 1.49 to 5.62). In this group, there was a RR for PDE5I of 1.40 (95 percent CI, 0.91 to 2.14) and a ratio of the rate ratios of 2.07 (95 percent CI, 1.05 to 4.11).

“In the prescription-odds weighted regressions, we found no association between PDE5I prescriptions and the risk of MI, suggesting that the TT prescription-related risk of MI is more likely a drug effect, rather than a result of behavioral or other factors associated with prescription,” the authors conclude. “Given the rapidly increasing use of testosterone therapy, the current results, along with other recent findings emphasize the urgency of the previous call for clinical trials adequately powered to assess the range of benefits and risks suggested for such therapy.”

The lead author is the owner of Consolidated Research; several coauthors are consultants to the company.