Testosterone is the key male sex hormone that regulates fertility, muscle mass, fat distribution, and red blood cell production.
When levels of testosterone drop below levels that are healthy, they can lead to conditions like hypogonadism or infertility. There are, however, sources from which people with low testosterone can boost their levels.
Low testosterone is becoming more and more common. The number of prescriptions for testosterone supplements has increased fivefold since 2012.
This article will explore what testosterone does and whether men should worry about decreasing levels of the hormone as they grow older.
Fast facts on testosterone
- Testosterone regulates a number of processes in the male body.
- Levels of testosterone tend to drop as men age.
- Prohormone supplements do not have any effect on testosterone levels.
- Testosterone supplements are prescribed only for specified conditions, and not to counteract the natural, age-related drop in testosterone levels.
- Testosterone replacement therapy (TRT) is also available. However, this can carry side effects and risks.
Testosterone is the hormone responsible for the development of male sexual characteristics. Hormones are chemical messengers that trigger necessary changes in the body. Females also produce testosterone, usually in smaller amounts.
It is a type of androgen produced primarily by the testicles in cells called the Leydig cells.
In men, testosterone is thought to regulate a number of functions alongside sperm production. These include:
- sex drive
- bone mass
- fat distribution
- muscle size and strength
- red blood cell production
Without adequate amounts of testosterone, men become infertile. This is because testosterone assists the development of mature sperm.
Despite being a male sex hormone, testosterone also contributes to sex drive, bone density, and muscle strength in women. However, an excess of testosterone can also cause women to experience male pattern baldness and infertility.
The brain and pituitary gland control testosterone levels. Once produced, the hormone moves through the blood to carry out its various important functions.
High or low levels of testosterone can lead to dysfunction in the parts of the body normally regulated by the hormone.
When a man has low testosterone, or hypogonadism, he may experience:
- reduced sex drive
- erectile dysfunction
- low sperm count
- enlarged or swollen breast tissue
Over time, these symptoms may develop in the following ways:
- loss of body hair
- loss of muscle bulk
- loss of strength
- increased body fat
Chronic, or ongoing, low testosterone may lead to osteoporosis, mood swings, reduced energy, and testicular shrinkage.
Causes can include:
- testicular injury, such as castration
- infection of the testicles
- medications, such as opiate analgesics
- disorders that affect the hormones, such as pituitary tumors or high prolactin levels
- chronic diseases, including type 2 diabetes, kidney and liver disease, obesity, and HIV/AIDS
- genetic diseases, such as Klinefelter syndrome, Prader-Willi syndrome, hemochromatosis, Kallman syndrome, and myotonic dystrophy
In women, however, high testosterone levels can lead to male pattern baldness, a deep voice, and menstrual irregularities, as well as:
- growth and swelling of the clitoris
- changes in body shape
- reduction in breast size
- oily skin
- facial hair growth around the body, lips, and chin
Recent studies have also linked high testosterone levels in women to the risk of uterine fibroids.
Testosterone imbalances can be detected with a blood test and treated accordingly.
Testosterone levels naturally decrease as a man ages.
The effects of gradually lowering testosterone levels as men age have received increasing attention in recent years. It is known as late-onset hypogonadism.
After the age of 40, the concentration of circulating testosterone falls by about 1.6 percent every year for most men. By the age of 60, the low levels of testosterone would lead to a diagnosis of hypogonadism in younger men.
Low testosterone has been associated with increased mortality in male veterans. Late-onset hypogonadism has become a recognized medical condition, although many of the symptoms are associated with normal aging.
The following are symptoms of late-onset hypogonadism:
- diminished erectile quality, particularly at night
- decreased libido
- mood changes
- reduced cognitive function
- fatigue, depression, and anger
- a decrease in muscle mass and strength
- decreased body hair
- skin changes
- decreased bone mass and bone mineral density
- increase in abdominal fat mass
As well as sexual dysfunction, late-onset hypogonadism has also been associated with metabolic disease and cardiovascular disease.
The degree to which testosterone levels decline varies between men, but a growing number of men experience the effects of reduced testosterone levels. Life expectancy has increased, and many men now live beyond the age of 60 years.
As a result, a higher number of men see the effects of age-related testosterone depletion.
Administering treatment for hypogonadism as the result of a disease differs from treating late-onset hypogonadism in older men.
One proposed treatment for low testosterone comes in the form of testosterone supplements.
One type of testosterone supplement, methyltestosterone, has received approval from the United States Food and Drug Administration (FDA). However, guidelines advise doctors not to prescribe this supplement due to the speed with which the liver metabolizes testosterone.
This can lead to liver toxicity. While doctors can legally prescribe the supplement, they generally try to avoid this.
Until stronger evidence is available to support the benefits and safety of testosterone supplementation, only older adults with severe clinical symptoms of low testosterone should be candidates for these supplements.
The FDA have advised that testosterone supplements are not suitable to treat late-onset hypogonadism, and a doctor should only prescribe them for an identifiable cause.
Testosterone replacement therapy
Testosterone replacement therapy (TRT) can help restore some affected functions of low testosterone.
Studies have shown that TRT mainly impacts bone strength and hemoglobin levels in the blood, but not mental sharpness.
The treatment can be administered by:
- skin gels and patches
- tablets that are absorbed through the gums
These can, however, trigger side effects, including:
- increased red blood cell count
- prostate and breast enlargement
- in rare cases, breathing difficulties during sleep
- increased risk of cardiovascular disease, although this is subject to debate
Deciding to pursue a course of TRT involves deciding between the perceived benefit of the therapy on the symptoms of a particular individual and the risks of the treatment.
However, the Endocrine Society advises that doctors should not prescribe TRT to men aged less than 65 years, even if they have low testosterone levels. The risks and suggested benefits of TRT for men younger than this are unclear, as are the benefits.
Current research is conflicting. Additional studies into testosterone replacement are necessary for physicians to fully understand its potential risks and benefits, and to identify the individuals that may see the most benefit.
Prohormone supplements and heart disease
Prohormones are a variety of steroid. They are often used to support weight loss and muscle-building.
A number of prohormone supplements are marketed at men to treat low testosterone levels. Such supplements can include dehydroepiandrosterone (DHEA), and the herbal product Tribulus terrestris. However, a bill was passed in 2014 banning designer anabolic steroids.
Legal variants have emerged since. However, there is little, if any, research to indicate that these prohormone supplements affect testosterone levels. Research from 2016 did not find any evidence that Tribulus terrestris, for example, can increase testosterone levels.
Such remedies may pose a risk to health. The law does not require herbal supplements to be proven safe before sale, so caution is advised.
The potential side effects of prohormones plus their unproven clinical benefits make them a poor, possibly dangerous choice for boosting testosterone.
For men, testosterone levels are important to maintain, but they naturally decrease over time. If symptoms of severe or chronic low testosterone are showing, the hormone deficiency may be caused by an active disease or condition.
Treatment can lead to unwanted side effects, so it can be crucial to balance the expected benefits of testosterone supplementation with the risks of the treatment. Often, low testosterone levels come without harmful physical effects and do not require treatment.
Speak to a medical professional, and confirm if treatment is required.