PHILADELPHIA – Testosterone gel for treatment of hypogonadism in older men boosted their left ventricular mass by 3.5% in a single year in the multicenter, double-blind, placebo-controlled Testosterone Cardiovascular Trial, although the clinical implications of this impressive increase remain unclear, Elizabeth Hutchins, MD, reported at the American Heart Association scientific sessions.
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Dr. Elizabeth Hutchins
“I do think these results should be considered as part of the safety profile for testosterone gel and also represent an interesting and understudied area for future research,” said Dr. Hutchins, a hospitalist affiliated with the Los Angeles Biomedical Research Center at Harbor-UCLA Medical Center.
The Testosterone Cardiovascular Trial was one of seven coordinated placebo-controlled, double-blind clinical trials of the impact of raising serum testosterone levels in older men with low testosterone. Some results of what are known as the TTrials have previously been reported (Endocr Rev. 2018 Jun 1;39[3]:369-86).
Dr. Hutchins presented new findings on the effect of treatment with 1% topical testosterone gel on body surface area–indexed left ventricular mass. The trial utilized a widely prescribed, commercially available product known as AndroGel. The study included 123 men over age 65 with low serum testosterone and coronary CT angiography images obtained at baseline and again after 1 year of double-blind testosterone gel or placebo. More than 80% of the men were above age 75, half were obese, more than two-thirds had hypertension, and 30% had diabetes.
The men initially applied 5 g of the testosterone gel daily, providing 15 mg/day of testosterone, with subsequent dosing adjustments as needed based on serum testosterone levels measured at a central laboratory. Participants were evaluated in office visits with serum testosterone measurements every 3 months. Testosterone levels in the men assigned to active treatment quickly rose to normal range and stayed there for the full 12 months, while the placebo-treated controls continued to have below-normal testosterone throughout the trial.
The key study finding was that LV mass indexed to body surface area rose significantly in the testosterone gel group, from an average of 71.5 g/m2 at baseline to 74.8 g/m2 at 1 year. That’s a statistically significant 3.5% increase. In contrast, LV mass remained flat across the year in controls: 73.8 g/m2 at baseline and 73.3 g/m2 at 12 months.
There was, however, no change over time in left or right atrial or ventricular chamber volumes in the testosterone gel recipients, nor in the controls.
Session comoderator Eric D. Peterson, MD, professor of medicine and a cardiologist at Duke University in Durham, N.C., said that “this is a very important topic,” then posed a provocative question to Dr. Hutchins: “If the intervention had been running instead of testosterone gel, would the results have looked similar, and would you be concluding that there should be a warning around the use of running?”
Dr. Hutchins replied that she’s given that question much thought.
“Of course, exercise leads to LV hypertrophy and we consider that to be good muscle, and high blood pressure leads to LV hypertrophy and we consider that bad muscle. So which one is it in this case? From what I can find in the literature, it seems that incremental increases in LV mass in the absence of being an athlete are deleterious. But I think we would need outcomes-based research to really answer that question,” she said.
Dr. Hutchins noted that this was the first-ever randomized controlled trial to measure the effect of testosterone therapy on LV mass in humans. The documented increase achieved with 1 year of testosterone gel doesn’t come close to reaching the threshold of LV hypertrophy, which is about 125 g/m2 for men. But evidence from animal and observational human studies suggests that even in the absence of LV hypertrophy, increases in LV mass are associated with increased mortality, she added.
She reported having no financial conflicts regarding her study, sponsored by the National Institutes of Health.
SOURCE: Hutchins E. AHA 2019, Session FS.AOS.04.