Testosterone Basics

The testes (testicles) make testosterone. Testosterone is the main sex hormone that men have. It controls male physical features. 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.

Women have testosterone too, but in much smaller amounts than in men.

Why is testosterone important?

What happens if testosterone levels are too low or too high?

How is testosterone status determined?

What should you know about testosterone testing?

Why is testosterone important?

Hormones are essential to reproductive health in all aspects of a man’s sexual life. The hypothalamus and pituitary gland are located at the base of the brain, and they work together to release hormones— luteinizing hormone (LH) and follicle stimulating hormone (FSH) —that stimulate the testes to produce testosterone and sperm. Testosterone, the main male hormone, helps maintain sex drive; vitality; sperm production; facial, pubic, and body hair; muscle; and bone.

What happens if testosterone levels are too low or too high?

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

Early symptoms (changes you feel) and signs (abnormalities that your doctor finds) of low testosterone in men include

  • A drop in sex drive
  • Weak erections
  • Infertility
  • Enlarged or tender breasts

Later, low testosterone can lead to decreased muscle and bone strength, less energy, and low sperm count.

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.

High testosterone

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 is testosterone status determined?

During a physical exam, your doctor will examine your body hair, size of your breasts and penis, and the size and consistency of the testes and scrotum. Your doctor may check for loss of side vision, which could indicate a pituitary tumor, a rare cause of low testosterone.

If you have symptoms of low testosterone, your doctor may suggest that you talk with an endocrinologist. This expert in hormones can help find the cause. Be open with your doctor about your medical history, all prescription and nonprescription drugs you are now taking, sexual problems, and any major changes in your life.

What should you know about testosterone testing?

Your doctor will also use blood tests to see if your total testosterone level is low. The normal range is generally 300 to 1,000 ng/dL, but this depends on the lab that conducts the test. To get a diagnosis of low testosterone, you may need more than one early morning (7–10 AM) blood test and, sometimes, tests of pituitary gland hormones.

For additional free patient resources visit the Hormone Health Network the nation’s endocrine patient education resource and find additional information on testosterone and much more:

Men’s Health

Male Hypogonadism

Male Infertility

Erectile Dysfunction

Decreased Libido

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