Low Serum Testosterone and Mortality - Part 1

Low Testosterone

Low serum testosterone is a common condition in aging associated with decreased muscle mass and insulin resistance.  Studies reveal that low testosterone levels are a risk factor for mortality in male veterans.  Declining testosterone levels in elderly men are thought to underlie many of the symptoms and diseases of aging.

One study evaluated testosterone levels in men older than 40 years.  Initial results of this study revealed that mortality was 34.9% higher in men with low testosterone levels.  After adjusting for age, medical morbidity, and other clinical factors, low testosterone levels continued to be associated with increased mortality.

In contrast to menopause, in which all women undergo a nearly complete cessation of gonadal estrogen production, in men, gonadal testosterone decreases progressively at a rate of 1.5% after the age of 30.  Manifestations of low testosterone include:

± Decreased muscle mass

± Declining bone mineral density (BMD)

± Increased fat mass and central obesity

± Insulin resistance

± Decreased libido and performance

± Decreased energy

± Increased irritability

Approximately 30% of men 60 years and older are believed to have low testosterone which is often accompanied by undesirable signs and symptoms such as low bone density and muscle mass, increased fat mass (especially central obesity), low energy, impaired physical, sexual and cognitive function.

Furthermore, other studies have revealed men with low testosterone are at increased risk of falls, low BMD, hip fracture, anemia, type-2 diabetes, depressive illness, systolic and diastolic blood pressure, fasting plasma glucose and serum insulin, triglycerides, an adverse metabolic risk profile, atherosclerosis and Alzheimer’s disease.  Low testosterone was found with some acute and chronic illnesses and certain medications.  Low testosterone predicted increased risk of cardiovascular and respiratory disease and mortality but was not significantly related to cancer deaths.

Total testosterone did not differ by smoking habits or exercise but was slightly lower among men who consumed at least 1 alcoholic drink daily.  Levels of testosterone were higher in men who lost 10 pounds or more in the past 10 years and low in men who had gained at least 10 pounds.  Total testosterone was 8% lower for men who had hypertension and 22% lower for men who had metabolic syndrome compared with men who did not.

One study revealed that low testosterone precedes the development of central obesity, metabolic syndrome and diabetes.  This study also revealed that lower total testosterone levels were associated with insulin resistance, altered lipid profile and high blood pressure.

Some of the adverse affects of male aging are attributed to the decrease in testosterone stimulating a surge of interest in testosterone therapy for middle-aged and older men.  Testosterone sales in the U.S. increased 20 fold in the 1990’s.

In a separate study, men in a geriatric rehabilitation unit with low testosterone were found to have an increased 6‑month mortality compared with men with normal testosterone levels who were of comparable age with comparable medical morbidity.

One particular study was based upon the evaluation of 794 men, aged 50–91 with a median age of 73.6 who had serum testosterone measurements between 1984 and 1987 and followed for mortality through July 2004.  The results revealed that in the 11.8 year follow-up, 538 deaths occurred.  Men whose total testosterone levels were in the lowest quartile (<241 ng/dL) were 40% more likely to die than those with higher levels, independent of age, adiposity, and lifestyle.  Additional adjustment for health status markers, lipids, lipoproteins, blood pressure and insulin, and estradiol levels had minimal effect on results.

Reviewing age, adiposity, and lifestyle-adjusted factors of cause-specific mortality, low and bioavailable testosterone were each significantly associated with an elevated 20-year risk of cardiovascular disease morbidity and death due to respiratory disease.

For more information or to read Part 2 of the series, please visit us at the Southwest Age Intervention Institute blog.