What Is Testosterone and Why Does It Decline?
Testosterone is a hormone. It’s what puts hair on a man’s chest. It’s the force behind his sex drive.
During puberty, testosterone helps build a man’s muscles, deepens his voice, and boosts the size of his penis and testes. In adulthood, it keeps a man’s muscles and bones strong and maintains his interest in sex. In short, it’s what makes a man a man (at least physically).
After age 30, most men begin to experience a gradual decline in testosterone. A decrease in sex drive sometimes accompanies the drop in testosterone, leading many men to mistakenly believe that their loss of interest in sex is simply due to getting older.
Women have testosterone too, but in much smaller amounts than in men.
Why is testosterone important for boys and men?
Testosterone helps bring on the physical changes that turn a boy into a man. This time of life is called puberty. Changes include
- Growth of the penis and testes
- Growth of facial, pubic, and body hair
- Deepening of the voice
- Building muscles and strong bones
- Getting taller
Men also need normal amounts of this hormone to make sperm and be able to have children.
How does testosterone work?
The brain and pituitary gland, a small gland at the base of the brain , control production of testosterone by the testes. From there, testosterone moves through your blood to do its work.
Your testosterone levels change from hour to hour. They tend to be highest in the morning and lowest at night.
Testosterone levels are highest by age 20 to 30 and slowly go down after age 30 to 35.
What can go wrong with testosterone levels?
For many reasons, testosterone can become—and stay—too low. Less often, testosterone levels can become too high. When this hormone is not in balance, health problems can result. Ask your doctor if you should get your testosterone level checked if you have any of the problems mentioned below. You can get treatment to fix hormone problems.
Low Testosterone: How Do You Know When Levels Are Too Low?
“A lot of the symptoms are mirrored by other medical problems,” Hedges says. “And for a long time, we were not attributing them to low testosterone, but to diabetes, depression, high blood pressure, and coronary artery disease. But awareness and appreciation of low testosterone has risen. We recognize now that low testosterone may be at the root of problems.”
Doctors will want to rule out any such possible explanations for symptoms before blaming them on low testosterone. They will also want to order a specific blood test to determine a man’s testosterone level.
Early symptoms (changes you feel) and signs (abnormalities that your doctor finds) of low testosterone in men include
Later, low testosterone can lead to decreased muscle and bone strength, less energy, and lower fertility.
Some things can temporarily lower testosterone, for instance, too much exercise, poor nutrition, or serious illness. Living a healthy lifestyle with regular exercise and a good diet helps maintain normal testosterone levels.
Low Testosterone: How Low Is Too Low?
The bottom of a man’s normal total testosterone range is about 300 nanograms per deciliter (ng/dL). The upper limit is about 800ng/dL depending on the lab. A lower-than-normal score on a blood test can be caused by a number of conditions, including:
- Injury to the testicles
- Testicular cancer or treatment for testicular cancer
- Hormonal disorders
- Chronic liver or kidney disease
- Type 2 diabetes
Some medicines and genetic conditions can also lower a man’s testosterone score. Aging does contribute to low scores. In some cases, the cause is unknown.
When young boys have too much testosterone, they can start puberty too early (before age 9). Some rare conditions, such as certain types of tumors, cause boys to make testosterone earlier than normal.
Young boys also can have too much testosterone if they touch testosterone gel that an adult man is using for treatment
How do you know what your testosterone level is?
To measure your testosterone level, your doctor can order a blood test. The test should be done in the morning between 7:00 and 10:00. If the result is not normal, you should repeat the test to make sure of the result. In healthy men, testosterone levels can change a lot from day to day, so a second test could be normal.
Words to know
a male sex hormone, such as testosterone.
a doctor who treats people who have hormone problems.
a chemical made in a gland in one part of the body. The hormone travels through the blood to another part of the body, where it helps other cells do their job.
a low testosterone level or sperm count, or both.
a hormone that affects and is made by the reproductive (sex) organs. It is responsible for secondary sex traits, such as facial hair in men.
Questions to ask your doctor
- Is my testosterone level normal?
- Do I need more tests?
- Do I need treatment?
- How long will I need treatment?
- Does the treatment have side effects?
- How often should I have check-ups?
- Should I see an endocrinologist for my care?