Testosterone

Testosterone is a hormone produced by the testicles and ovaries. It’s considered a sex hormone because it helps your body develop male or female traits and controls things like puberty and libido. Levels of testosterone are naturally much higher in males. But women make testosterone, too.

Your body naturally produces testosterone. Sometimes, your body may make too much or too little. When this happens, it can disrupt certain bodily processes or cause symptoms.

Testosterone is also available in synthetic (man-made) forms. These versions mimic the effects of natural testosterone. Healthcare providers may use them to treat or manage certain medical conditions.

What does testosterone do?

Testosterone is the main male sex hormone. The process of making testosterone begins before birth — as early as seven weeks in fetal development. A gene on the Y chromosome starts the growth of testicles in men. The testicles start producing testosterone. Testosterone helps form male reproductive organs before birth, including the prostate, penis and scrotum.

During puberty, testosterone is responsible for many of the changes seen in boys, like:

• Increased height and muscle mass (growth spurts)
• Body and pubic hair growth
• Deepening of their voice
• Growth of their penis and testicles
• Increased sex drive (libido)

Testosterone is also essential for sperm production. It helps signal your body to make new red blood cells, too. And in adult males, it continues to play a role in maintaining muscle mass, bone strength and sex drive.

Testosterone in women

Women have much smaller amounts of testosterone. Most of it gets changed into estradiol, the main female sex hormone. Testosterone in women helps support sex drive, energy, mood, and bone and muscle strength.

Where is testosterone produced?

The testicles (in men) and ovaries (in women) produce testosterone. Your adrenal glands also produce small amounts of testosterone in both sexes.

Your hypothalamus and pituitary gland control the amount of testosterone your gonads (testicles or ovaries) produce and release. Your hypothalamus releases gonadotropin-releasing hormone (GnRH), which triggers your pituitary gland to release luteinizing hormone (LH). LH travels to your gonads and stimulates the release of testosterone.

As testosterone increases, it blocks the gonadotropin-releasing hormone, which helps maintain normal levels of testosterone.

Any problem with this process can lead to abnormally high or low testosterone levels.

What causes high testosterone levels?

Several conditions can cause your body to produce too much testosterone, including:

• Ovarian or testicular tumors: These tumors release excess testosterone.
• Adrenal tumors: Adrenal tumors are rare tumors that make too much testosterone.
• Polyendocrine metabolic ovarian syndrome (PMOS): Formerly called polycystic ovary syndrome (PCOS), this happens in women when their ovaries create excess androgens (testosterone).
• Congenital adrenal hyperplasia: In congenital adrenal hyperplasia (CAH), genetic changes affect enzymes in your adrenal glands. When these enzymes don’t work properly, your body makes too much testosterone.

In adult women, high testosterone can lead to:

• Irregular periods
• Acne
• Increased body hair
• Thinning hair

In adult men, high testosterone can lead to:

• Acne
• Aggression or mood changes
• Increased muscle mass

High testosterone in children can lead to precocious (early) puberty in both sexes. In girls, it can also lead to an abnormally large clitoris (it may look like a penis).

What happens when testosterone levels are too low?

Lower-than-normal testosterone levels typically only cause obvious symptoms in men. This condition is called male hypogonadism. It’s when low testosterone is due to an underlying medical condition or damage to your testicles, pituitary gland or hypothalamus.

The symptoms of low testosterone vary based on your age.

Low testosterone in fetal development

Low testosterone levels in fetal development can affect the development of male reproductive organs (fetal hypogonadism). A rare condition called androgen insensitivity syndrome (AIS) happens when a person who is genetically male doesn’t develop external male genitals because their bodies can’t respond to testosterone. AIS can cause problems during puberty, as well as infertility as an adult.

Low testosterone in puberty

Testosterone deficiency in puberty can lead to:

• Less voice deepening
• Slowed growth in height
• Reduced development of pubic hair
• Reduced growth of their penis and testicles
• Lower-than-normal strength and endurance

Low testosterone in adult men

Testosterone levels in men naturally decline with age. But adult males can have lower-than-typical testosterone levels. This can happen due to conditions such as obesity, Type 2 diabetes, chronic illness, or problems with the testicles or pituitary gland.

Symptoms can include:

• Loss of muscle mass and an increase in body fat
• Loss of body hair
• Depressed mood
• Erectile dysfunction
• Low sex drive
• Weak bones
• Difficulty with concentration and memory

Testosterone replacement therapy (TRT) is one of the main treatment options for low testosterone. It works by replacing the testosterone your body isn’t making enough of. The goal is to bring testosterone levels back into a healthy range and improve your symptoms.

Low testosterone in women

Low testosterone in women doesn’t have clear signs or symptoms as it does in men. You may feel low sex drive or low energy if your testosterone levels are low. This is partly because estrogen is the main sex hormone in women.

How is testosterone tested?

If a healthcare provider suspects you may have irregular testosterone levels, they may order one or more tests, including:

• Total testosterone blood test (this is usually done in the morning, as testosterone levels are highest then)
• Follicle-stimulating hormone (FSH) blood test
• Luteinizing hormone (LH) blood test

What are normal testosterone levels?

Testosterone levels are measured in nanograms per deciliter (ng/dL). Normal ranges can vary based on the type of blood test done and the laboratory. Your provider will always reference normal ranges when giving your results. Talk to them if you have questions.

Normal testosterone levels for men

Age plays a role in normal testosterone levels. Testosterone levels begin low in children (less than 25 ng/dL). Levels increase around puberty and peak around age 18. They can reach up to over 1,000 ng/dL. Then, levels decline as you reach your 40s.

Here’s a list of what normal ranges look like for men:

• Age 20 to 24: 409 to 558
• Age 25 to 29: 413 to 575
• Age 30 to 34: 359 to 498
• Age 35 to 39: 352 to 478
• Age 40 to 44: 350 to 473

Normal testosterone levels for women

Women naturally have less testosterone than men. In general, women have anywhere between 15 to 46 ng/dL. Testosterone levels are highest around age 20 and decline naturally with age.

How is testosterone used in medical treatments?

Anabolic steroids are medications that are man-made (or synthetic) forms of testosterone. They act like testosterone in your body and come in different forms, including injections, gels, implantable pellets and skin patches.

Healthcare providers may prescribe them for health conditions like low testosterone. In this case, it can help improve symptoms like low sex drive and loss of muscle mass.

But some athletes and bodybuilders misuse man-made testosterone by taking very high doses to boost performance and build muscle. This can raise testosterone levels far beyond typical levels. Misusing testosterone can lead to serious long-term health problems.