Older age not main cause of testosterone decline in healthy men

Issue: August 2011

ENDO 2011

BOSTON — A decline in testosterone levels as men grow older is likely the result, but not the cause, of deteriorating general health, Australian researchers said.

In a new study, the researchers found that age alone had no effect on testosterone levels in healthy, older men.

These are the first results released from the Healthy Man Study, according to principal researcher David Handelsman, MD, PhD, professor and director of the ANZAC Research Institute at the University of Sydney.

“We had originally expected age to have an effect on serum testosterone, so the findings were a bit of a surprise,” Handelsman said in a press release issued at the meeting.

Researchers at two study centers in Australia recruited 325 men (mean age, 60 years) who had self-reported excellent health and no symptom complaints. They took blood samples from the men nine times during 3 months to test serum testosterone levels.

Serum testosterone levels did not decline with increasing age (P=.76) in this group of healthy, asymptomatic men. Obesity and fasting, however, were associated with a mild, but clinically unimportant, lowering of serum testosterone levels. When the researchers measured dihydrotestosterone, they found that serum levels increased with age and fasting, but decreased with obesity. Serum estradiol increased with fasting, but did not vary with age or obesity.

“These findings suggest that fasting systematically overestimates ambient serum testosterone, dihydrotestosterone and estradiol, and the modest age-related decline in blood testosterone associated with nonspecific symptoms may be due to accumulating comorbidities of aging rather than representing an androgen deficiency state contributing to adverse health features of male aging,” the researchers wrote in the study abstract.

The message for physicians and patients is that “older men with low testosterone levels do not need testosterone therapy unless they have diseases of their pituitary or testes,” Handelsman said in the release.

For more information:

Satorius G. OR35-1. Presented at: The Endocrine Society 93rd Annual Meeting & Expo; June 4-7, 2011; Boston.

Disclosure: Dr. Handelsman reports no relevant financial disclosures. The research was supported by the Medical Benefits Fund Foundation in Sydney, part of the private health insurer Bupa.

A report by Australian investigators confirms a recent study that found morning testosterone levels are about 10% higher if drawn in a fasting state compared with a non-fasting state. It is likely that most normal ranges have utilized early morning samples from men who were not asked to fast; the question of should we routinely require patients to fast before providing blood specimens for testosterone assays will need to be addressed. This issue should be incorporated into the CDC-Endocrine Society program to develop a common reference standard and more uniform normal ranges for testosterone assays.

These investigators recruited men who reported that they were healthy. While they confirmed the widely accepted finding that testosterone levels are lower in obese men, they did not observe an age-related fall in serum total testosterone levels. It may be that an age-related fall in total testosterone levels was masked by an age-related increase in sex hormone-binding globulin levels. If so, this should be accompanied by an age-related decrease in free or bioavailable testosterone levels.

Does aging in the absence of low testosterone levels or apparent disease cause decreased energy, libido and mood, erectile dysfunction, increased osteoporosis, decreased strength and physical function? Multiple chronic diseases, as well as testosterone deficiency in younger men, are accompanied by these symptoms. The Australian investigators have characterized the hormonal status of their men better than most population-based reports, so it will be of considerable interest to know the prevalence of these symptoms in this population.

If their healthy older men are able to maintain normal total and free testosterone levels and are relatively free of these symptoms, this should encourage healthier lifestyles. While we know that this is desirable, only a small percentage of our population seem committed to this approach to good health. Another approach to this issue is to provide testosterone treatment to symptomatic older men with subnormal testosterone levels. The Testosterone Trial, which is ongoing, should provide definitive answers to this question.

- Glenn R. Cunningham, MD
Endocrine Today Editorial Board member

Follow EndocrineToday.com on Twitter.