Injected TRT earns high marks for safety, effectiveness

A newly published review suggests that age-related testosterone deficiency treatment with intramuscular injections of testosterone replacement therapy (TRT) offers health benefits and lower cardiovascular risk compared to testosterone replacement by patch or gel.

READ: Studies examine risk factors for low, high T

While TRT can result in increased muscle mass and strength, decreased fat mass, and increased bone mineral density, the therapy has known risks. These include the development of polycythemia, decreases in high-density lipoprotein cholesterol, breast tenderness and enlargement, and prostate issues.

The authors point out, however, that TRT does not increase prostate cancer risk. And whether TRT hurts, helps, or has no effect on cardiovascular risk remains controversial in the literature.

The University of Florida, Gainesville, researchers who conducted this latest review were among the authors of a previously published study suggesting that oral TRT increases cardiovascular risk, but no significant cardiovascular effects were noted with injected or transdermal TRT (BMC Med 2014; 12:211).

For the current study, which was published online in the American Journal of Physiology – Endocrinology and Metabolism (April 21, 2015), study authors Stephen E. Borst, PhD, and Joshua F. Yarrow, PhD, reviewed literature indicating “that intramuscular injected TRT produces greater musculoskeletal benefits and lower cardiovascular risk compared to transdermal TRT… We also review the literature discussing the use of 5α-reductase inhibitors as a promising means of improving the safety profile of TRT.”

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According to the authors, for older hypogonadal men, administering TRT by injection, versus orally or transdermally, offers greater musculoskeletal benefits because doses are higher by injection. But while doses are higher when injected, intramuscular TRT might be less likely to result in cardiovascular risks than transdermal TRT. This could be because transdermal testosterone results in greater serum dihydrotestosterone (DHT) elevation, due to significant expression of 5α-reductase in skin-not muscle.

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More research is needed to determine TRT’s cardiovascular effects, but there are data pointing to trends indicating that TRT might not accelerate underlying early-stage prostate cancer; transdermal TRT may result in cardiovascular risk; and intramuscular injected TRT may provide cardiovascular benefit, the authors wrote.

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More research also is needed to determine the safest and most effective TRT administration for older hypogonadal men. For now, the authors suggest intramuscular injected testosterone with finasteride (Proscar) could be the best approach. That’s because several studies demonstrate the combination approach produces musculoskeletal benefits without the prostate enlargement that results from testosterone alone.

“Finasteride produces relatively few adverse events and may also produce cardiovascular benefits and/or reduce prostate cancer by reducing DHT,” they wrote.

“While further research is needed, it appears at this time that I.M. injected T plus finasteride may be both the safest and most effective treatment for older hypogonadal men,” they concluded.

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