Australian scientists recently studied testosterone and its progression in males from young to old age and discovered that a gradual decline in testosterone levels is caused by both men's lifestyles as well as aging.
The findings were presented at the Endocrine Society's 94th annual meeting that took place recently in Houston.
The Endocrine Society focuses on the research of hormones and the practice of endocrinology.
Many older men are known to have diminished levels of the sex hormone testosterone.
Even though the cause is debated, some population-based studies have found that changes in testosterone levels are similar among men of the same age over time.
It is common knowledge that declining testosterone levels are an inevitable part of the aging process.
However, there may be more to this condition than mere aging.
Study co-author Dr. Gary Wittert, professor of medicine at the University of Adelaide in Australia, stated that the choices men make also plays a more significant role in lowered testosterone levels than previously thought.
Testosterone changes are also explained by smoking behavior and changes in health status, particularly obesity and depression.
The study was supported by the National Health and Medical Research Council of Australia.
The researchers measured testosterone levels in over 1,500 men during two clinical visits over five years.
The blood testosterone samples were tested at the same time for each visit.
In analyzing the data, the investigators made the study more accurate and empirical by excluding men who had abnormal lab values, who were taking medications, or who were noted to have medical conditions that affected hormones.
In total, 1,382 men were included in the study, with an average age of 54 and an age range of 35 to 80 years.
Overall, testosterone levels did not drop significantly over the five years.
The testosterone levels were found to decrease by less than one percent each year.
When the scientists examined the data regarding subgroups, they discovered that specific factors were related to lower testosterone levels five years later than at the beginning of the study.