(RxWiki News) Testosterone is a vital hormone for many of the processes that happen in men's bodies. Levels of this hormone in old age might be a sign of survival.
A recent study found that older men with midrange levels of testosterone had the lowest death rates of any cause.
The researchers concluded that additional research could help identify ways to use information from sex hormone levels to help men maintain good health as they grow older.
"Discuss your hormone levels with a doctor."
The lead author of this study was Bu B. Yeap, from the School of Medicine and Pharmacology at the University of Western Australia in Perth, Australia and the Department of Endocrinology and Diabetes of the Fremantle Hospital in Fremantle, Australia.
The study used data collected from the Health in Men Study (HIMS) — a population-based study of men between the ages of 70 and 89 from Perth, Australia.
Yeap and colleagues selected 3,690 men who did not have a history of prostate cancer, did not have a current or past history of using hormone therapy and had no history of orchidectomy (surgical removal of the testicles).
The participants had been assessed for hypertension (high blood pressure), dyslipidemia (abnormal amount of fat in the blood) and diabetes. The researchers also looked at death, hospital and cancer records from a countrywide database.
The presence of heart disease was determined by self-report during HIMS and hospital records. Blood samples had been collected to determine levels of testosterone (T) annd dihydrotestosterone (DHT).
DHT is a type of testosterone that is responsible for most of male puberty characteristics, such as muscular growth, facial and body hair growth and deepening of the voice.
Yeap and colleagues considered outside factors that might have influenced death such as age, education level, smoking history, body mass index (height to weight ratio) and waist-to-hip ratio.
After follow-up, the findings showed that 974 (26 percent) of the participants had died. Ischemic heart disease (buildup in arteries surrounding heart blocking blood flow) caused 325 of theses deaths.
The researchers found that the men who died of any cause were on average older, less likely to have finished high school, more likely to have a history of smoking and more likely to have a lower BMI at the beginning of HIMS than the men who survived.
Men who died of any cause also were more likely to have dyslipidemia, heart disease or cancer, as well as higher levels of creatinine at wave 1 of HIMS compared to the men who survived.
The men who died were found to have lower levels of testosterone, DHT and estradiol at baseline than the men who survived.
The researchers found that the men who died of ischemic heart disease (IHD) had a higher occurrence of dyslipidemia, diabetes and heart disease, a lower occurrence of cancer and higher creatinine levels than the men who died of non-IHD causes.
The men were categorized in four different levels of testosterone, with the first level representing the lowest amount of testosterone and the fourth level representing the highest amount of testosterone.
The highest all-cause and IHD death rates were among men who had the lowest testosterone levels (first level), representing 31 percent of all deaths. The second highest death rates were among men with the highest testosterone levels (fourth level), representing 27 percent of all deaths.
The findings showed that the men with testosterone levels in the middle range (second and third levels) had the lowest all-cause death rates.
There was an 18 percent decreased risk of all-cause death among those with the second level of testosterone compared to those with the fourth level of testosterone, and a 22 percent decreased risk of all-cause death among those with the third level of testosterone versus first level.
The men also were categorized according to four different levels of DHT that represented the same scaling as the testosterone levels — first level was the lowest and fourth level was the highest.
There was a 42 percent decreased risk of IHD death for men with the third level of DHT compared to those with first level, and a 31 percent decreased risk for those with the fourth level of DHT compared to those with the first level of DHT.
The findings revealed that the levels of testosterone among the IHD deaths were similar to those among all-cause deaths, but were not statistically significant. Therefore, IHD deaths were significantly associated with DHT levels only.
The researchers also determined that estradiol levels were not associated with either cause of death.
The associations between testosterone and DHT for all-cause death, and DHT for IHD deaths, were independent of age, being overweight and other considered risk factors.
The researchers concluded that health professionals should monitor testosterone levels in older men because they may be a sign of survival. DHT should also be monitored if there is a risk for IHD, according to the researchers.
The authors noted a few limitations of their study.
First, HIMS was an observational study so the researchers were limited in determining cause-and-effect factors associated with death and hormone levels, and could not account for any possible deaths due to complications from treatments or medications.
Second, the study population may have been over representative of healthier men so the findings may not be applicable to all older men.
Third, the study only involved a single blood sample. Fourth, the participants were mostly Caucasian so the findings may not be applicable to other races and ethnicities.
This study was published online on November 20 in The Journal of Clinical Endocrinology & Metabolism.
The National Health and Medical Research Council of Australia provided funding.