Testosterone: Everything You Need to Know

Testosterone is the primary sex hormone in men, and it is responsible for the development of many of the 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,  testosterone sends signals to a male’s testicles (or to a woman’s ovaries) that spark feelings of sexual desire. (1)

In males, testosterone plays an important role in puberty, the time when a young man reaches sexual maturity and he can reproduce. The following changes typically happen during this life stage: (2)

• 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: (1)

• 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

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. (3)

Lifestyle factors also affect testosterone production, including exercising too much or not eating a healthy diet.

How Can You Tell if Testosterone Levels Are High, Low, or Normal?

Your doctor can order a blood test to find out if your testosterone levels are in the normal range. (1)

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. (5) Low T can also be caused by other issues, including certain medications and being overweight.

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

In men who are middle-aged and beyond, symptoms may include: (6)

• 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. (1)

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. Testosterone levels tend to be highest early in the morning in young men, although this isn’t necessarily the case in older men. (5)

What Are the Options if Your Testosterone Levels Are Low?

Testosterone replacement therapy is currently only FDA-approved for men who have been diagnosed with hypogonadism. The use of testosterone therapy is increasingly common in the United States, with more than two million men receiving the therapy. Not every man benefits from taking testosterone replacements. Testosterone is available in different forms, including topicals such as gels, creams, and patches; injections; and pellets that are surgically placed directly beneath the skin. (7)

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

Possible long-term effects of TRT have not yet been established, but there is scientific evidence to suggest it may have an impact on cardiovascular health, cancers of the prostate and breast, and sleep disturbances such as sleep apnea. (8) There is also a risk of polycythemia, which in turn increases risk for blood clots and stroke.

People who take testosterone should seek medical attention immediately if symptoms of a heart attack or stroke are present, such as: (9)

• Chest pain
• Shortness of breath or trouble breathing
• Weakness in one part or one side of the body
• Slurred speech

Learn More About Testosterone Replacement Therapy

Women’s bodies don’t produce as much testosterone as men’s. The 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. (10)

Related: Testosterone: Is It Time for Women to Get Their Own Formulation for Low Libido?

Women can have health issues as a result of either low or high testosterone levels. Some postmenopausal women experience dips in testosterone levels that can cause a decrease in sex drive. Low testosterone levels can also cause other health issues such fatigue, and increased risk for bone loss, osteoporosis, and fractures. (11)

High Testosterone Levels Can Cause Problems in Women

But when a premenopausal woman’s testosterone levels are too high, it can lead to polycystic ovary syndrome (PCOS), a condition that increases the risk of irregular or absent menstrual cycles, infertility, excess hair growth, skin problems, and miscarriage. High levels of testosterone in women, whether caused by PCOS or by another condition, can cause serious health conditions such as insulin resistance, diabetes, high cholesterol, high blood pressure, and heart disease. (12)

The FDA has not approved the use of testosterone therapy in women, and in their most recent guidelines, the Endocrine Society recommends against the general use of testosterone therapy in healthy women for the treatment of the following conditions: (13)

• Infertility
• Sexual dysfunction other than hypoactive sexual desire disorder (HSDD)
• Cognitive function
• Cardiovascular health
• Metabolic syndromes
• Bone health
• General well-being

Learn More About Testosterone and Women’s Health

While the testosterone supplementation industry is somewhat controversial in the United States, there are many well-established drug-free ways to maintain healthy testosterone levels.

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. Libido levels can be affected by factors such as medication, relationship quality, fatigue, and disease, as well as issues such as anxiety, stress, and depression.

While a change in interest and desire for sex may signal a medical problem or side effect, it’s not considered a red flag. 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

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

Favorite Orgs and Pages for Essential Testosterone Facts and Stats

Hormone Health Network From the Endocrine Society

The Endocrine Society is the world’s largest and most influential organization of endocrinologists (doctors who treat hormone disorders). The Hormone Health Network provides online resources for patients, including information on men’s health and low testosterone. The site also contains an up-to-date physician referral directory with more than 6,500 Endocrine Society member doctors.

American Society for Reproductive Medicine

This society of fertility specialists maintains a patient-focused website with easy-to-read educational pages on reproductive health topics, including testosterone use and male infertility. The site also contains resources for finding a reproductive health professional.

American Urological Association (AUA)

The AUA, which represents urologists and urologic health professionals, publishes guidelines on the diagnosis and treatment of testosterone deficiency.

Choosing Wisely

Choosing Wisely is an initiative of the American Board of Internal Medicine that aims to promote conversations between patients and their doctors about unnecessary medical tests, treatments, and procedures. Along with the AUA, they’ve compiled a list of 15 things physicians and patients should question, including the prescription of testosterone to men with erectile dysfunction but normal testosterone levels.

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. duathalete 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 The Body Issue — 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

Talking About Men’s Health

This blog was one of the top 10 men’s health blogs in 2018. Topics vary from natural remedies to help fight hair loss to what you need to know about testosterone replacement therapy.

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, The Turek Clinic

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.

Where to Find Testosterone Clinical Trials

Clinical trials are medical studies aimed at preventing, diagnosing, and treating diseases. Check here for clinical trials on male infertility, andropause, low T, and other testosterone-related disorders:

• Antidote
• CenterWatch
• ClinicalTrials.gov
• Program for Healthy Volunteers
• Research Match
• Science 37