According to the National Spinal Cord Injury Statistical Center at the University of Alabama at Birmingham, the estimated number of people living with a spinal cord injury (SCI) in the United States in 2014 was 276,000. The annual incidence of SCI in the United States is approximately 12,500 new cases each year, not including those who die at the scene of an accident. Approximately 80% of SCI occurs among males.1
Hypogonadism in men, defined as the reduction or absence of testosterone secretion or other physiological activities of the testes, appears to be common among young men with chronic SCI, according to Shannon D. Sullivan, MD, of MedStar Washington Hospital Center in Washington D.C.2
“Depending on how one defines low testosterone, we found that between 35% and 65% of young men with SCI, ages 18 to 50 years, have low testosterone. [This] is much higher than the general population of men of that age. Per NHANES data, 2.3% to 8.7% of the general male population between ages 18 and 50 has low testosterone,” said Dr. Sullivan.
“Testosterone levels are not routinely checked in men with SCI, [so] unfortunately it is impossible to know whether rates of low testosterone are changing. It is likely that the rates are staying the same, however. More and more men are living longer with chronic SCI, so more and more men will naturally be affected as our care for SCI victims improves.”
A Potential Connection
At the Endocrine Society’s 95th Annual Meeting and Expo, held in San Francisco from June 15 to 19, 2013, Sullivan and colleagues presented two studies showing that not only was hypogonadism common among young men with SCI, but it was also associated with increased cardiometabolic risk.
“We found a significantly higher prevalence of low testosterone in men with SCI compared to age-matched controls. The etiology was usually ‘secondary hypogonadism,’” said Sullivan.
“We found significant correlations between low testosterone levels and several cardiometabolic risk markers in men with chronic SCI. Specifically, lower testosterone was associated with higher Framingham Risk Scores, increased percent body fat, lower serum HDL levels, higher levels of inflammatory markers (CRP and IL-6) and higher insulin resistance in this population, indicating that low testosterone may contribute to increased cardiovascular disease risk seen in men with SCI after injury.”
Dr. Sullivan said that the data suggest a link between SCI and hypogonadism in men.
“The cause seems to be central. That is, that the insult is at the level of the hypothalamus and/or pituitary, not an insult directly to testosterone production by the testes. It is not clear at this point that the level of spinal cord injury or the severity of injury plays a role, but we hypothesize that more complete spinal cord damage and more severe injuries lead to higher risk of low testosterone,” said Dr. Sullivan.