Medical journals have reported trials that examine the benefits and harms of taking testosterone for men over 65 with low blood levels of testosterone (less than 275 ng/dL). At 12 study sites across the country, a total of 790 participants were given testosterone gel or a placebo applied daily to the skin. Most of these men had low testosterone due to aging, not due to damage to the testicles or brain where testosterone levels are controlled. Over a year, investigators measured the effects of testosterone on:
• bone density and strength
• heart health
• cognitive function
• sexual function
Bone Density and Strength: Testosterone increased bone density and strength in 200 older low-testosterone men (JAMA Intern Med, February 21, 2017). These increases were greater in the spine than in the hips.
Anemia: Testosterone raised hemoglobin levels by at least 1 g/dL in nearly 130 men with anemia (JAMA Internal Medicine, Feb 21, 2017).
Heart Health: Testosterone increased plaques significantly in the arteries leading to the heart likely to increase risk for heart attacks (JAMA, 2017;317(7):708-716). However, another study of more than 44,000 men with low testosterone showed that three years of testosterone gel reduced heart attack rate by 25 percent compared to those given placebos (JAMA Internal Medicine, Feb 21, 2017). The effects of testosterone on heart attack risk are controversial.
Cognitive Function: Testosterone did not improve memory or other brain functions including verbal memory, visual memory, executive function or spatial ability in 500 men with age-associated memory loss (JAMA, 2017;317(7):717-727).
Sexual Function: Improvement in sexual function is the benefit most strongly supported by research studies. However, having low testosterone levels does not determine whether a man will respond to erection-increasing drugs such as tadalafil in older men with enlarged prostates and erectile dysfunction (J Sex Med, May 2016;13(5):843-51).
A review of several other studies showed that testosterone gel can improve depression, bone mineral density, energy, libido, erectile function, muscle mass, insulin resistance, and lower urinary tract symptoms (Curr Opin Urol, Mar 2016;26(2):152-7). Testosterone treatment did not appear to increase a man's risk of developing an enlarged prostate.
Testosterone Is Often Given to Men Who Will Not Benefit from its Use
A study from Baylor Medical School shows that more than 85 percent of men treated with testosterone do not have any disease caused by low testosterone. Most of the men suffer from adult-onset hypogonadism associated with chronic medical conditions such as diabetes, metabolic syndrome, arteriosclerosis and obesity. They do not have a deficiency of testosterone caused by damaged testicles or brain hypothalamic and pituitary glands that cause low testosterone. They should be treated for these conditions and not take testosterone, which may increase their risk for future heart attacks (Mayo Clinic Proceedings, June 24, 2016).
• Men with normal blood levels of testosterone (>300) should not take testosterone since it may increase risk for heart attacks, liver damage and shutting down their own natural production of testosterone.
• Older men with normal testicles and brain hormones should not take testosterone unless their testosterone is very low (below 150).
• Usually men should take testosterone if they have low levels of the brain hormones that stimulate the testicles to produce testosterone or testicles that are damaged so they cannot make testosterone.
• Most men who suffer from poor sexual function because they have conditions that damage their sexuality, such as overweight, diabetes, arteriosclerosis or other life-shortening conditions that affect sexual function, should work to reverse those conditions rather than resorting to testosterone.
• Testosterone pills can damage the liver, so if a man chooses to take testosterone, the form of choice is a gel that is absorbed through the skin so it avoids the liver.