Mention “T” and an Englishman might anticipate an afternoon beverage, and golfers may check the time when their foursome is to leave the clubhouse. But these days many men who hear that word will think you’re talking about testosterone replacement. At least 2.3 million testosterone prescriptions per year are written for men, and the use of testosterone in older men is expected to rise, given current trends.
Male aging is accompanied by decreases in lean muscle mass and strength, bone mineral density, energy and sexual function. Increases in fat mass are also noted. Older men may be diagnosed with hypogonadism, and increasing numbers are being prescribed testosterone therapy.
Research published in the New England Journal of Medicine this week by Joel Finkelstein and colleagues at Massachusetts General Hospital provides a more detailed insight into the different roles of testosterone and estradiol in the body composition, strength and sexual function of men. NEJM Deputy Editor Dr. Julie Ingelfinger said, “This study is important because it dissects the roles of both testosterone and estrogen in male body composition, strength and sexual function.”
All 400 participants took goserelin acetate to suppress endogenous hormones. Of the 400 men, 198 were randomly assigned to get either placebo gel or testosterone gel (doses of 1.25 g, 2.5 g, 5 g or 10 g) for 16 weeks. Another 202 men used the placebo gel or testosterone gel and anastrozole to suppress conversion of testosterone to estradiol. The investigators examined the changes in the percentages of body fat and in less mass as primary outcomes. The men were also assessed for subcutaneous- and intraabdomenal- fat areas, thigh muscle area and strength and sexual function.
Body fat percentages increased in men who used the placebo or testosterone (1.25 g of 2.5 g) without the anastrozole daily. Lean mass and thigh-muscle area decreased in men who got placebo and in those getting 1.25 g of testosterone without anastrozole. Leg-press strength declined only among those getting placebo. Sexual desire declined as the testosterone dose decreased.
The authors suggest that their results may have important clinical implications — providing a physiological basis for interpreting testosterone levels in young and middle-aged men and, perhaps providing guidance for replacement regimens in aging men.
The findings also hint at the medical complications that might develop at different gonadal steroid levels. The findings about the visceral fat increases are important because such increases are associated with diabetes and the metabolic syndrome. Likewise, the increase in intraabdominal fat with aromatase inhibition might imply that there would be an increase in cardiovascular disease if long-term estrogen deficiency exists. The authors also suggest that testosterone supplementation might be justified in men whose serum testosterone levels are lower than 200 ng per deciliter. The study highlights the important role of estrogen in regulation of body fat and sexual function. Other studies have already shown the importance of estrogen in bone mineralization.
In summary, this study suggests that the roles of both hormones merit increased attention, as both impact factors important for the health of aging men. Prospective, randomized trials on the effects of testosterone and/or estrogen supplementation over time would be important. Men may need to be concerned about both T and E.