What comes to mind when you think of testosterone? Macho Man? Aggressive, impatient, type A behavior? Violence? Testosterone’s role in bad behavior is largely a myth. What’s more, testosterone plays other important roles in health and disease that may surprise you. For example, did you know that testosterone is a key player in prostate cancer? Or that women need testosterone too?
What is testosterone?
Testosterone is the major sex and sex hormone in men and plays a number of important roles such as:
- Development of the penis and testicles
- Deepening of the voice during adolescence
- Adolescent appearance of facial and pubic hair
- Possible baldness later in life
- muscle size and strength
- Bone growth and strength
- Sex drive (libido)
- sperm production
Adolescent boys with too little testosterone may not experience normal masculinization. For example, the genitals may not grow, facial and body hair may be insufficient, and the voice may not normally deepen.
Testosterone can also help maintain normal mood. This hormone may have other important functions that have yet to be discovered.
Signals sent from the brain to the pituitary gland at the base of the brain control testosterone production in men. The pituitary gland then signals the testicles to produce testosterone. A “feedback loop” closely regulates the amount of hormones in the blood. When testosterone levels get too high, the brain sends signals to the pituitary to decrease production.
If you think that testosterone is only important in men, you are wrong. Testosterone is produced in the ovaries and adrenal gland. It is one of the few androgens in women. These hormones are thought to have important effects on:
- ovarian function
- bone strength
- sexual behavior, including normal libido
Proper balance between testosterone (along with other androgens) and estrogen is important for the normal functioning of the ovaries. While the specifics are unclear, it’s also possible that androgens play an important role in normal brain function (including mood, sex drive, and cognitive function).
Do you know?
Testosterone is synthesized in the body from cholesterol. But having high cholesterol doesn’t mean your testosterone will be high. Testosterone levels are very carefully controlled by the pituitary gland in the brain for this to happen.
Effects of testosterone excess
Having too much natural testosterone is not a common problem among men. But things like anger, especially in men, can be attributed to testosterone by many people. Part of this may be due to the difficulty of defining “normal” testosterone levels and “normal” behavior.
Testosterone levels in the blood change dramatically over time and even within a day. Additionally, what appears to be a symptom of testosterone excess (see below) may actually be unrelated to this hormone.
In fact, most of what we know about abnormally high testosterone levels in men comes from athletes who use anabolic steroids, testosterone, or related hormones to increase muscle mass and athletic performance.
Problems associated with abnormally high testosterone levels in men include:
- Low sperm count, shrinking testicles, and impotence (looks weird, right?)
- Heart muscle damage and increased risk of heart attack
- Enlarged prostate with difficulty urinating
- liver disease
- acne (pimples)
- Fluid retention with swelling in the legs and feet
- Weight gain is perhaps partially associated with increased appetite.
- high blood pressure and cholesterol
- insomnia disease
- increased muscle mass
- increased risk of blood clots
- Stunted growth in adolescents
- Uncharacteristic aggressive behavior (not clearly proven)
- Mood swings, euphoria, irritability, impaired judgment, delusions
Perhaps the most common cause of high testosterone levels among women is a disease called polycystic ovary syndrome (PCOS) . This disease is common. It affects 6% to 10% of premenopausal women. Women with PCOS have more than one ovarian cyst in their ovaries .
Symptoms include irregular menstrual periods, decreased fertility, excess or coarse hair on the face, extremities, trunk and groin area, male pattern baldness, darkening of the skin, thick skin, weight gain, depression, and anxiety.
One treatment available for many of these problems is spironolactone, a diuretic (water pill) that blocks the action of male sex hormones. Women with high testosterone levels due to illness or drug use may experience reduced breast size and deepened voice, in addition to many of the problems men may have.
Effects of testosterone deficiency
In recent years, researchers (and pharmaceutical companies) have focused specifically on the effects of testosterone deficiency in men. In fact, as men age, testosterone levels drop very gradually, about 1% to 2% each year, in contrast to the relatively rapid decline in estrogen that causes menopause in women.
The testicles produce less testosterone, there are fewer signals from the pituitary to tell the testes to make testosterone, and a protein (called sex hormone-binding globulin) increases with age.
All this reduces the active (free) form of testosterone. More than a third of men over the age of 45 may have lower-than-normal testosterone levels (though, as noted, defining optimal testosterone levels is difficult and somewhat controversial).
Symptoms of testosterone deficiency in adult men include:
- reduced body and facial hair
- loss of muscle mass
- low libido, impotence , small testicles, decreased sperm count and infertility
- increased breast size
- hot flashes
- Irritability, poor concentration, and depression
- shedding of body hair
- Brittle bones and increased risk of fracture
Some men with testosterone deficiency have symptoms or conditions related to their low testosterone that will improve when they receive testosterone replacement. For example, a man with osteoporosis (bone loss) and low testosterone can improve bone strength and reduce the risk of fractures with testosterone replacement.
Surprisingly, women may be troubled by testosterone deficiency symptoms. For example, disease in the pituitary gland can cause decreased testosterone production. They may experience low libido, decreased bone strength, poor concentration, or depression.
Do you know?
There are times when low testosterone isn’t such a bad thing. The most common example is probably prostate cancer. Testosterone can stimulate the prostate gland and the growth of prostate cancer. This is why drugs that lower testosterone levels and castration are common treatments for men with prostate cancer.
Men receiving testosterone replacement should be carefully monitored for prostate cancer . Although testosterone makes prostate cancer grow, it is not clear that testosterone therapy actually causes cancer.
Diseases and conditions that affect testosterone
Men may experience a decrease in testosterone due to conditions or diseases that affect:
- Conditions originating from the testicles: Direct injury of the testicles, castration, infection, radiation therapy, chemotherapy, tumors
- Conditions originating from the pituitary and hypothalamus gland: Tumors, drugs, HIV/AIDS , certain infections, and autoimmune diseases
Genetic diseases such as Klinefelter syndrome (where a man has an extra X chromosome) and hemochromatosis (where an abnormal gene causes excess iron to build up in the body, including in the pituitary gland) can also affect testosterone.
In addition to having the ovaries removed, women may have a testosterone deficiency due to diseases of the pituitary, hypothalamus, or adrenal glands. Estrogen therapy increases sex hormone-binding globulin and, like aging men, this reduces the amount of free, active testosterone in the body.
Currently, testosterone therapy is primarily approved for the treatment of delayed male puberty, low testosterone production (due to failure of the testicles, pituitary or hypothalamus function), and some inoperable breast cancers in women .
However, testosterone therapy is quite likely to improve symptoms in men with significantly low levels of active (free) testosterone, such as:
- generalized weakness
- low energy
- Disable vulnerability
- Problems with sexual function
- problems with cognition
However, many men with normal testosterone levels have similar symptoms, so the direct link between testosterone levels and symptoms isn’t always clear. As a result, there is some controversy over which men should be treated with additional testosterone.
People with normal testosterone levels are sometimes treated with testosterone on the advice of their doctor or take the medication themselves. Others have also recommended it as a “cure” to aging.
For example, a 2003 study from Harvard Medical School found that even among men who started treatment with normal testosterone levels, there was fat loss, increased muscle mass, better mood, and less anxiety while taking testosterone therapy. ( Source )
Similar observations were noted among women. However, the risks and side effects of taking testosterone if the body is already producing enough still discourage supplemental use of testosterone.
As a result
Testosterone is an even more important hormone than many people realize. Men and women need the appropriate amount of testosterone for normal development and many functions. However, the optimal amount of testosterone is still not clearly understood.
Checking testosterone levels is as easy as getting a blood test. The hard part is interpreting the result. Levels change throughout the day. In the absence of symptoms, a single low level may be meaningless, especially if it is normal at another time.
We need more research to know when to measure testosterone, how best to respond to the results, and when it may be helpful to accept the risks of treatment.