New research published in Sexual Medicine provides insights into specific testosterone formulations and their long-term effects on men’s health.
Testosterone therapy is usually prescribed to men with hypogonadism and signs or symptoms associated with low testosterone. Hypogonadism may be caused by problems in the testes (the glands that produce the hormone) or areas of the brain responsible for triggering production. Some doctors also prescribe it for men experiencing symptoms of age-related testosterone declines, like low sexual desire, fatigue, and erectile dysfunction.
Men can receive testosterone therapy in a variety of ways, including gels applied to the skin, injections into a muscle, and pellets that are implanted under the skin every few months. While these methods are effective and have been approved by the U.S. Food and Drug Administration (FDA), long-term data directly comparing the effects of different formulations are lacking.
To learn more, researchers from Baylor College of Medicine in Houston, Texas recruited 178 men with low testosterone for a three-year study. Specifically, the research team looked at three typical delivery methods:
• Testosterone gel, applied to the skin once daily (47 men)
• Self-injections, once weekly (57 men)
• Pellets implanted under the skin, every three to six months (74 men)
“Our goal was to assess the unique and common effects of each [testosterone] formulation in order to better inform selection of [testosterone] formulations for individual patients,” the authors wrote.
At baseline and every three to six months, the researchers measured total testosterone, calculated free testosterone, estradiol, hemoglobin, hematocrit, prostate-specific antigen (PSA), total cholesterol, triglycerides, LDL cholesterol, and HDL cholesterol.
Therapy raised the testosterone levels of all the men, but those receiving injections had the biggest increases.
Levels of estradiol, a type of estrogen, also increased for all the men, although this only occurred for the first six months for men using pellets. Increases were more significant for men using injections and gels. The researchers suggested that this increase was due to aromatization – the natural conversion of testosterone into estrogen. (Men whose estradiol levels were too high underwent aromatase inhibitor therapy to bring those levels back to normal.) However, it was not clear whether high estradiol levels are a concern, the researchers noted.
None of the men had significant PSA increases with any formulation, even if they had a history of prostate cancer.
Levels of hemoglobin and hematocrit were assessed with erythrocytosis in mind. Erythrocytosis is an increase in red blood cells, a condition which requires monitoring to prevent levels from becoming too elevated. In this study sample, erythrocytosis rates were higher in men receiving testosterone injections. Erythrocytosis also started earlier for men on injections than for men using gels or pellets. The authors added that testosterone levels were higher in the injection group and this might explain the higher rates of erythrocytosis. But they were not sure whether peak testosterone levels or overall levels were contributing factors.
Finally, lipid levels (total cholesterol, triglycerides, LDL cholesterol, and HDL cholesterol) were analyzed. No significant differences were found among the groups. The authors acknowledged that patients did not always fast before levels were tested and their diets were not tracked – two factors that could have affected the results.
Pastuszak, Alexander W., MD, PhD
“Comparison of the Effects of Testosterone Gels, Injections, and Pellets on Serum Hormones, Erythrocytosis, Lipids, and Prostate-Specific Antigen”
(Full-text. First published online: August 12, 2015)