What is testosterone?

Testosterone is often called the “male” hormone. However, both men and women produce this hormone. Hormones are molecules that regulate the body. They are usually produced in one location in the body and travel to other organs. Other hormones in the body include growth hormone and thyroid-stimulating hormone.

Testosterone is an androgen hormone. It produces male characteristics in the body. Testosterone is made in the following locations:

  • testes in men
  • ovaries in women
  • the adrenal glands, located above the kidneys in both men and women

Men have higher levels of testosterone in their bodies than women do. In either sex, if testosterone levels become imbalanced, adverse symptoms can occur.

Testosterone is responsible for many actions in the male body throughout a man’s life cycle. It helps the external and internal organs of a male fetus develop. This includes the male reproductive organs such as the penis and testicles. During puberty, testosterone is responsible for:

  • growth spurts
  • deepening of the voice
  • growth of hair in the pubic region, face, and underarms

Testosterone is also associated with behaviors such as aggression and sexual drive. Men need testosterone to make sperm for reproduction.

In women, testosterone also contributes to a woman’s sex drive. It also helps to secrete hormones important in a woman’s menstrual cycle.

Testosterone also plays common roles for both sexes. For example, the hormone stimulates the body to make new red blood cells. Testosterone can also affect a man’s bone density, fat distribution, and muscle strength.

Low testosterone in men can cause many physical symptoms. It can also cause insulin resistance, which can contribute to diabetes. Examples of symptoms caused by low testosterone in men include:

  • decreased sex drive
  • erectile dysfunction
  • higher percentage of stomach fat
  • gynecomastia (development of breast tissue)
  • infertility
  • lack of body hair
  • lack of deepening of the voice
  • low muscle mass
  • slowed growth of the testicles or penis

A boy will typically start puberty at around age 10. If this is delayed, low testosterone levels could be the cause. Possible causes of low testosterone in men include:

  • chronic health conditions such as diabetes
  • damage to the testes, such as from physical trauma, alcoholism, or viral illnesses
  • genetic diseases, including Klinefelter, Kallman, or Prader-Willi syndromes
  • hypothalamic disease or tumor
  • pituitary disease or tumor
  • testicular failure

Symptoms and causes of low testosterone in women

In women, low testosterone can result in:

  • decreased sex drive
  • infertility
  • irregular or absence of menstrual periods, known as amenorrhea

Low testosterone in women can be caused by:

  • long-term use of oral contraceptives
  • old age
  • ovarian failure or removal of both ovaries

In both genders, low testosterone levels can cause mood changes such as:

  • lack of motivation
  • depression
  • difficulty concentrating
  • problems with memory
  • insomnia

Having too much testosterone can also cause health problems.

Excess testosterone in males

In boys, undergoing early puberty, also called precocious puberty, can cause development of:

  • facial hair
  • deepening of the voice
  • well-developed muscles
  • growth of the sexual organs

Early puberty can be caused by tumors and a condition known as congenital adrenal hyperplasia.

Potential causes of excess testosterone in men include:

  • congenital adrenal hyperplasia
  • taking anabolic steroids
  • tumors of the testicles or adrenal glands

Excess testosterone in women

In women, excess testosterone can cause a condition known as hirsutism. This causes a woman to develop body hair in a male fashion, including on the face. Virilization is another condition caused by excess testosterone. This causes a woman to have a masculine appearance. Symptoms can include male pattern baldness and a deep voice.

Ovary or adrenal gland tumors and polycystic ovarian syndrome are potential causes.

Taking certain medications can increase testosterone levels in both men and women. Examples of these medications include:

  • anticonvulsants
  • barbiturates
  • clomiphene
  • estrogen therapy

Talk to your doctor before you stop taking any medications.

A man’s testosterone levels will typically peak somewhere between age 20 and 30. After this time, they will gradually decrease for the rest of his life. Testosterone levels are estimated to decrease by 1 percent annually after age 30 to 40. Therefore, lower testosterone levels are more common among older men. This explains some of the age-related changes in men, such as loss of muscle mass.

Women’s testosterone levels peak in their 20s and then begin to slowly decline. When a woman starts to experience menopause, her testosterone levels are half of what they were at their peak. A woman’s adrenal glands will make less testosterone during menopause. The ovaries will continue to produce testosterone after menopause but stop producing estrogen and progesterone. Most age-related changes in women are caused by a lack of estrogen and progesterone.

Treating the condition that is causing high or low testosterone levels can help restore levels. But it’s not always possible to find a cause of testosterone imbalances. Your doctor can prescribe testosterone replacement to correct low levels.

There are several treatments for hypogonadism or low testosterone. Examples include:

  • topical gels
  • patches
  • injectable testosterone
  • implantable testosterone

Both men and women may take testosterone therapy. A woman may take testosterone to improve sex drive and reduce sexual dysfunction. However, women must have an appropriate level of estrogen before treatment. This is because testosterone can affect a woman’s estrogen levels.

Testosterone replacement therapy (TRT) can cause side effects, such as:

  • acne
  • breast tenderness or enlargement
  • increased amount of red blood cells
  • infertility
  • small testicles
  • swelling of the low extremities

You should have regular checkups with your doctor while undergoing TRT. This is to make sure your levels are increasing as they should.

Some older men with healthy testosterone levels take the supplement to increase strength and energy. But current research doesn’t support that testosterone supplements can provide these effects in men with healthy levels.