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What is testosterone?
Testosterone is a vital sex hormone that plays an important role in puberty. But contrary to what some people believe, testosterone isn’t exclusively a male hormone. Women produce small amounts of it in their bodies as well. In men, testosterone is produced in the testes, the reproductive glands that also produce sperm. The amount of testosterone produced in the testes is regulated by the hypothalamus and the pituitary gland.
What is a hormone?
Hormones, such as testosterone, are powerful chemicals that help keep our bodies working normally. The term hormone is derived from the Greek word, hormo, which means to set in motion. And that’s precisely what hormones do. They stimulate, regulate, and control the function of various tissues and organs. Made by specialized groups of cells within structures called glands, hormones are involved in almost every biological process, including sexual reproduction, growth, metabolism, and immune function. These glands, including the pituitary, thyroid, adrenals, ovaries and testes, release various hormones into the body as needed.
Do testosterone levels diminish with age? Does “male menopause occur?”
There is scant evidence that “male menopause,” a condition supposedly caused by diminishing testosterone levels in aging men, exists. As men age, their testes often produce somewhat less testosterone than they did during adolescence and early adulthood, when production of this hormone peaks. But it is important to keep in mind that the range of normal testosterone production is large. Many older men have testosterone levels within the normal range of healthy younger men. Others have levels well below this range. However, the likelihood that a man will ever experience a major shut down of hormone production, similar to a woman's menopause, is remote.
In fact, many of the changes that take place in older men often are incorrectly blamed on decreasing testosterone levels. Some men who have erectile difficulty (impotence), for instance, may be tempted to blame this problem on lowered testosterone. However, in many cases, erectile difficulties are due to circulatory problems, not low testosterone.
Who might benefit from testosterone therapy?
Testosterone therapy remains a scientifically unproven method for preventing or relieving any physical or psychological changes that men with normal testosterone levels may experience as they get older. Except for a relatively few younger and older men with extreme deficiencies, testosterone treatment is not deemed appropriate for most men at this time. For the few men whose bodies make very little or no testosterone—for example, men whose pituitary glands have been destroyed by infections or tumors, or whose testes have been damaged—supplements in the form of patches, injections, or topical gel may offer substantial benefit. Supplements may help a man with exceptionally low testosterone levels maintain strong muscles and bones and increase sex drive.
However, more research is needed to determine what, if any, effects testosterone replacement may have in healthy older men without these extreme deficiencies. For now, the risks and benefits of testosterone therapy for most men who do not have extreme deficiencies of the hormone are unknown, and there is insufficient evidence for making well-informed decisions on whether this therapy is suitable in these individuals.
What are some of the risks of using testosterone therapy?
Investigators are concerned about the long-term harmful effects that supplemental testosterone might have on the aging body. It is not yet known, for instance, if testosterone supplements increase the risk of prostate cancer, the second leading cause of cancer death among men. In addition to potentially promoting new prostate cancers, testosterone also may promote the growth of those that have already developed. Studies also suggest that supplementation might trigger excessive red blood cell production in some men. This side effect might thicken blood and increase a man's risk of stroke.
I know someone who uses testosterone therapy and he says he feels stronger and more “alive” than he has in years. Is there any scientific evidence to support this claim?
Although some older men who have tried these supplements report feeling "more energetic" or "younger,” testosterone supplementation remains a scientifically unproven method for preventing or relieving any physical and psychological changes that men with normal testosterone levels may experience as they get older. Until more scientifically rigorous studies are conducted, the question of whether the benefits of testosterone replacement outweigh any of its potential negative effects will remain unanswered.
So what is the NIA doing to find out more about the risks and benefits of testosterone therapy?
For more than a decade, the National Institute on Aging (NIA), a component of the Federal government’s National Institutes of Health, has supported and conducted studies of replenishing hormones and similar substances to find out if they may help reduce frailty and improve function in older people.
The NIA, for instance, is investigating the role of testosterone supplementation in delaying or preventing frailty. Results from preliminary studies involving small groups of men have been inconclusive, and it remains unclear to what degree supplementation of this hormone can sharpen memory or help men maintain stout muscles, sturdy bones, and robust sexual activity.
Why did the NIA and the National Cancer Institute ask the Institute of Medicine (IOM) for recommendations about testosterone therapy?
In 2002, the NIA and the NCI requested that the IOM conduct a 12-month study to:
- Review and assess current knowledge about the risks and benefits of testosterone therapy in older men.
- Prepare an evidence-based report and make recommendations regarding the design, safety, and ethics of clinical trials of this intervention, including whether such studies are even warranted.
This IOM Committee was conceived, in part, because of growing concerns about an increase in the number of older men apparently using testosterone replacement therapy (TRT) in the absence of adequate scientific information about its risks and benefits.
Many questions remain about the use of this hormone in late life. It is unclear, for example, whether men who are at the lower end of the normal range of testosterone production would benefit from supplementation. It was hoped that the Committee could recommend ways to conduct clinical trials of testosterone in this population.
What kinds of medical specialists served on this committee?
The Committee was comprised of prominent scientists specializing in epidemiology, endocrinology, geriatrics, urology, oncology, psychiatry and other relevant fields.
What did the IOM Committee conclude? What were its recommendations?
Until the safety and efficacy of testosterone therapy is older men is established, the Committee said that—outside of clinical trials—supplements of this hormone are only appropriate for indications approved by the FDA (the primary indication is hypogonadism in men who make little or no testosterone). Testosterone therapy, the Committee concluded, is inappropriate for widespread, generalized use to prevent possible age-related diseases or for enhancing strength or mood in otherwise healthy older men.
Specifically, the Committee made five major recommendations:
- Conduct clinical trials in older men with low testosterone levels. These trials should be designed to assess if testosterone therapy is an effective treatment in these individuals. Establish a clear benefit before assessing long-term risks.
- Begin with short-term, randomized, double-blind placebo-controlled efficacy trials in symptomatic older men with low testosterone levels to determine the potential risks and benefits. The participants should be 65 and older and have testosterone levels below the physiologic levels of young adult men. Results should be measured in four areas: weakness/frailty/disability; sexual dysfunction; cognitive dysfunction; and well-being/quality of life.
- Conduct longer term studies if short-term efficacy is established. Studies to determine long-term risks and benefits should be conducted only if clinically significant benefit is established in the initial trials.
- Ensure the safety of participants. The Committee recommended a system for minimizing risk and protecting participants in clinical trials of testosterone therapy.
- Conduct further research. In addition to the recommendation regarding clinical trials, the Committee also suggested additional research, particularly regarding age-related changes in testosterone levels.