TUESDAY, June 5, 2007 (HealthDay News) -- Men 50 and older with low levels of testosterone may be at higher risk of dying within 20 years than men with higher levels of the male hormone, a new study suggests.
But, the researchers stressed, more studies are need to examine the potential link, and there's nothing to indicate that testosterone supplements would reduce the risk of death.
For the study, Gail Laughlin, an assistant professor of family and preventative medicine at the University of California, San Diego, and colleagues followed almost 800 men, aged 50 to 91, for 18 years as part of the "Rancho Bernardo Study," looking at the relationship between serum testosterone levels and mortality.
They found that men with low testosterone had a 33 percent higher risk of dying from any cause than men with either normal or elevated testosterone levels. This link stood up regardless of age, physical activity, or lifestyle -- including smoking and drinking. But the link grew weaker when adjusted for metabolic syndrome and inflammatory biomarkers such as interleukin-6 and C-reactive protein, Laughlin said.
Metabolic syndrome is a condition defined by a constellation of risk factors for cardiovascular disease, such as high blood pressure, high blood glucose, and a waist diameter greater than 40 inches in men.
The study authors concluded that the relationship between low testosterone levels and mortality "is explained in part by the metabolic syndrome, and is dependent on the association of low testosterone levels with elevated markers of inflammation."
The findings were to be presented Tuesday at the Endocrine Society's annual meeting, in Toronto.
Dr. Glenn Braunstein, chairman of medicine at Cedars-Sinai Medical Center in Los Angeles, called the study "very interesting." But he noted that drawing conclusions from a single testosterone reading can be misleading, because the hormone's levels fluctuate throughout the day. "So taking a single testosterone level and extrapolating from that is not the be-all and end-all," he said.
Braunstein also noted that a number of factors, including disease, infection, and weight, can lower testosterone levels.
Dr. Anne Cappola, assistant professor of medicine and epidemiology at the University of Pennsylvania School of Medicine, said it's possible that testosterone itself may not be the culprit in the new study but rather an indication of some other inflammatory condition.
"It is hard to know the chicken and the egg," Cappola said. "Does low testosterone cause inflammation or is inflammation leading to low testosterone? In this study, you can't necessarily tear that apart."
Laughlin stressed that as an epidemiological observation, her study did not uncover whether low testosterone levels actually cause increased risk of death or are simply a marker of some other disease process. So, no man should take the results to mean he should take testosterone supplements to reduce the risk of death.
"We cannot recommend that any man take testosterone based on these results," she said. "We need randomized, placebo-controlled trials to see if it is effective, and also if it is safe. Proposals for those studies are under way."
This study isn't the first to link low testosterone levels to mortality. Last year, researchers at the University of Washington, Seattle, and the Veterans Administration Puget Sound Health Care System found that low testosterone levels were associated with an 88 percent increased likelihood of death in men over 40.
According to Laughlin, the difference between the two studies is that the earlier research looked at younger men who were in poor to bad health -- they were seeking medical care. "Our study was a population of relatively healthy men living in a community, who were older on average, and when we excluded those with known cardiovascular disease or diabetes, we still saw the association between low testosterone levels and increased risk of mortality over the following 20 years," she said.
To learn more about the endocrine system and hormones, visit The Hormone Foundation.