Men's Health

Testosterone: Everything You Need to Know

Cathy Garrard
By
Elise M. Brett, MD
by

What Are the Functions of Testosterone After Puberty?

Explore the importance of testosterone in men’s health and its role in regulating various bodily functions post-puberty.
What Are the Functions of Testosterone After Puberty?

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You likely know of the testosterone hormone for its role in sexual desire or growing facial hair, but this key chemical performs many other important functions, such as signaling blood cell production and ensuring bone health.

And while it’s true that men’s testosterone levels gradually decline as they age, there are cases where testosterone levels can be abnormally low and cause negative symptoms. If necessary, there are ways to increase testosterone through lifestyle changes and hormone replacement therapy.

Keep reading to learn more about this important hormone and how it relates to your health.

What Is Testosterone?

Testosterone is the primary sex hormone in men, and it is responsible for the development of many physical characteristics that are considered typically male. Women also produce the hormone in much smaller amounts. Testosterone, part of a hormone class known as androgens, is produced by the testicles after stimulation by the pituitary gland, which is located near the base of the brain. Among other functions, the testosterone hormone sends signals to a male’s testicles (or to a woman’s ovaries) that spark feelings of sexual desire.

The Role of Testosterone in Male Development and Health

In males, the testosterone hormone plays an important role in puberty, the time when a young man reaches sexual maturity and can reproduce. The following changes typically happen during this life stage:

  • The penis and testicles grow
  • Facial, pubic, and body hair develop
  • The voice deepens
  • Muscles and bones become stronger
  • Height increases
After puberty, testosterone helps regulate the following bodily functions:

  • Production of red blood cells
  • Bone density
  • Fat distribution
  • Muscle strength and mass
  • Growth of facial and body hair
  • Sperm production
  • Sex drive

Learn More About Testosterone and Men’s Health

What Causes Testosterone Levels to Decrease?

Testosterone levels gradually drop in men as a natural part of aging. By age 45, it starts falling by about 1 percent a year, but it is widely accepted that levels may start to decline when a man is in his thirties.

Lifestyle and body composition factors can also affect testosterone production. Smoking, obesity, lack of regular exercise, and low muscle mass can contribute to low testosterone levels.

If you’re curious about your testosterone levels, your doctor can order a blood test to find out if your testosterone levels are in the normal range.

What Is Low Testosterone, or “Low T”?

In some cases, low testosterone (also known as low T) may be caused by a medical condition known as hypogonadism, which occurs when the body does not generate normal amounts of the hormone. It happens when there is a problem with the testicles or the pituitary gland that creates an inability to produce normal amounts of testosterone.

Symptoms of so-called low T vary depending on the cause of the problem and the age when it happens.

In men who are middle-aged and beyond, symptoms may include:

  • Low energy and depressed mood
  • Sleep disturbances
  • Low sex drive
  • Problems getting or maintaining an erection
  • Low sperm count
  • Loss of muscle and bone strength
Not all men with age-related low testosterone will experience any symptoms, and others aren’t bothered by them. Troubles with energy, sleeping, and mood can also be caused by other issues like medication side effects or excessive alcohol use.

How Do Doctors Test for and Diagnose Hypogonadism?

Hypogonadism (as well as age-related low testosterone) is diagnosed with blood tests that measure the level of testosterone in the body. The Endocrine Society recommends testing for suspected low T with a total testosterone test. It should be performed on two separate occasions, early in the morning and on an empty stomach.

What Are the Options if Your Testosterone Levels Are Low?

The best-known treatment for low testosterone is testosterone replacement therapy (TRT), which is available as injections, pills, topical gels/creams, nasal gels, and pellets that are surgically placed directly beneath the skin.

The use of testosterone therapy is increasingly common in the United States, with more than two million men receiving the therapy, but many of these cases are off-label prescriptions for age-related testosterone decline.

That said, it’s important to note that the U.S. Food and Drug Administration (FDA) has only approved TRT for men who have been diagnosed with hypogonadism, and the effectiveness and safety of TRT treatment for age-related decline are still being debated. Several medical organizations, including the Endocrine Society and the American Society for Clinical Pathology, do not recommend prescribing TRT unless there is laboratory evidence of testosterone deficiency.

What Are the Side Effects of Testosterone Replacement Therapy (TRT)?

Researchers are still investigating the possible side effects and risks of TRT, but evidence suggests they include:

One risk of TRT is venous thromboembolism (VTE), which refers to blood clotting that starts in a vein. A study of almost 40,000 participants found that men taking TRT, whether for hypogonadism or other reasons, had a short-term increased risk of developing VTE. This correlation was especially true for men younger than 65.

 VTE can manifest as pulmonary embolism (PE), where a blood clot travels, gets stuck in the lungs, and restricts oxygen and blood supply to the lungs. PE is very serious and can lead to heart failure and death.

Additionally, the effect of TRT on heart health has long been a subject of debate, but more recent data suggests that TRT does not increase cardiovascular risk. In a randomized, double-blind, placebo-controlled study published in 2023, more than 5,000 patients with hypogonadism who were diagnosed with or had a high risk of cardiovascular disease were prescribed a daily testosterone gel or a placebo for an average of 1.8 years. The resulting rates of major, adverse, cardiac events were very similar, with 7 percent of the TRT group and 7.3 percent of the placebo group experiencing an event.

Learn More About Testosterone Replacement Therapy

What About Testosterone in Women’s Health?

Women’s bodies don’t produce as much testosterone as men’s. The testosterone hormone is generated in the ovaries and adrenal glands. Women need small amounts of it as part of the mix of hormones that keep mood, energy levels, sex drive, and bodily functions running smoothly.

Women can have health issues as a result of either low or high testosterone levels. Some women experience a decrease in sex drive as a result of the normal reduction in testosterone that occurs with age.

 In addition, low testosterone in women can cause tiredness, loss of strength, trouble conceiving, and irregular menstrual cycles, among other symptoms. The best way to know your testosterone level is to talk to your doctor about doing a blood test.


But when a premenopausal woman’s testosterone levels are too high, it is often the result of polycystic ovary syndrome (PCOS), a condition that is associated with irregular or absent menstrual cycles, infertility, excess hair growth, skin problems, and miscarriage.

Can Women Undergo Testosterone Replacement Therapy (TRT)? 

The FDA has not approved the use of testosterone therapy in women. According to a global position statement by the Endocrine Society and 10 other global medical societies, the use of TRT in women is only supported for those with hypoactive sexual desire disorder/dysfunction (HSDD), which is an absence of sexual desire or fantasies that causes significant distress or interpersonal difficulties.

Even then, the authors state that TRT should only be prescribed after other possible causes of HSDD are explored and treated. The safety of long-term TRT use in women has not been established, and there is insufficient data to support the use of TRT in women for any other condition or symptom, per the statement.

Learn More About Testosterone and Women’s Health

Is There a Natural Way to Enhance Testosterone Levels?

In an attempt to remedy testosterone decline, some people turn to supplements that claim to increase testosterone levels, sometimes called “T boosters.” However, there is very little clinical evidence that these supplements work, and the FDA doesn’t regulate dietary supplements for safety or effectiveness.

One investigation of 50 testosterone supplements found that only about 25 percent of them had data-supported ingredients that may boost testosterone. Furthermore, about 10 percent of them had ingredients that may negatively affect testosterone, and some supplements contained doses of vitamins and minerals that were over the tolerable limit.

However, many healthy lifestyle changes may improve testosterone levels, including:

  • Improving diet
  • Increasing muscle mass through cardio and strength training
  • Getting more sleep
  • Reducing stress levels
  • Addressing health conditions like diabetes, sleep apnea, metabolic syndrome, and obesity

Is Your Libido Healthy and Normal? Is Your Sexual Desire Lacking?

Sex drive is a nonclinical term that means enthusiasm or interest in sexual activity. The presence of it (or lack thereof) can indicate the state of your mental and physical functioning.

What controls the sex drive is a very complex intertwining of biological, psychological, and social-cultural influences. In men and some women, libido is closely associated with testosterone levels, but other factors may play a role, such as medication, relationship quality, fatigue, disease, anxiety, stress, and depression.

While a change in interest and desire for sex may signal a medical problem or side effect, it’s normal for libido to fluctuate throughout life. If you consider your libido levels too low or too high, treatments are available.

Learn More About the Role of Testosterone in Sex Drive and Overall Health

 

Resources About Testosterone

This is a selective list of online resources to provide information, support, and searchable databases on testosterone health and testosterone disorders.

Favorite Resources for Becoming an Advocate

Partnership for the Accurate Testing of Hormones (PATH)

PATH formed in 2010 to help the clinical, medical, and public health communities improve patient care through more accurate and reliable hormone tests. PATH supports research that improves the diagnosis and treatment of hormone disorders, including a landmark 2017 study that defines the “normal” range of testosterone in young adult men.

National Center for Transgender Equality

This nonprofit was founded by transgender activists in 2003 to advocate for transgender equality, including the rights of people seeking hormone therapy and other transition-related medical procedures and treatments.

Transathlete

This site, founded by U.S. duathlete Chris Mosier — the first openly trans man to make a U.S. Men’s National Team in 2015 and the first transgender athlete to feature in a Nike commercial and ESPN The Magazine — offers a list of policy resources for transgender athletes of all ages and abilities undergoing hormonal treatment with testosterone or testosterone suppression therapy.

Favorite Blogs

MenAlive

Jed Diamond, author of Male Menopause and Surviving Male Menopause, blogs about critical aspects of health and well-being for men over 40.

Dr. Turek’s Blog

Paul Turek, MD, a urologist in San Francisco, is an international leader in male fertility research. He blogs about men’s health topics, including steroids, testosterone, and male infertility, on the Turek Clinic’s website.

Editorial Sources and Fact-Checking

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Sources

  1. Could You Have Low Testosterone? MedlinePlus. May 12, 2023.
  2. Puberty. MedlinePlus. December 27, 2016.
  3. Travison TG et al. A Population-Level Decline in Serum Testosterone Levels in American Men. The Journal of Clinical Endocrinology & Metabolism. January 2007.
  4. Ko DH et al. Prevalence of Low Testosterone According to Health Behavior in Older Adults Men. Healthcare. January 2021.
  5. Kumar P et al. Male Hypogonadism: Symptoms and Treatment. Journal of Advanced Pharmaceutical Technology & Research. July–September 2010.
  6. What Is Low Testosterone?  Urology Care Foundation.
  7. Bhasin S et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology & Metabolism. May 2018.
  8. Petering RC et al. Testosterone Therapy: A Review of Clinical Applications. American Family Physician. October 1, 2017.
  9. Testosterone Therapy: Potential Benefits and Risks as You Age. Mayo Clinic. January 19, 2024.
  10. Walker RF et al. Association of Testosterone Therapy With Risk of Venous Thromboembolism Among Men With and Without Hypogonadism. JAMA Internal Medicine. February 2020.
  11. Venous Thromboembolism. Cleveland Clinic. February 22, 2022.
  12. Lincoff AM et al. Cardiovascular Safety of Testosterone-Replacement Therapy. The New England Journal of Medicine. July 13, 2023.
  13. Miller KK et al. Patient Guide to Therapeutic Use of Androgens in Women. The Journal of Clinical Endocrinology & Metabolism. October 1, 2006.
  14. Decreased Desire. The North American Menopause Society.
  15. Low Testosterone in Women. Cleveland Clinic. April 12, 2023.
  16. Davis SR et al. Global Consensus Position Statement on the Use of Testosterone Therapy for Women. The Journal of Clinical Endocrinology & Metabolism. October 2019.
  17. Clemesha CG et al. Testosterone Boosting’ Supplements Composition and Claims Are Not Supported by the Academic Literature. The World Journal of Men’s Health. January 2020.
  18. McCallum K. 5 All-Natural Ways to Boost Your Testosterone. Houston Methodist. April 9, 2021.
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