What Does Testosterone Do? Function, Benefits, and Risks Explained

You’ve probably heard about testosterone, but do you know exactly what it does in your body? This hormone, produced primarily in the testes in men and ovaries in women, acts as a master regulator of sexual development, muscle mass, bone density, and even mood. Here’s what the science says about its roles in both men and women, the signs of low levels, and what you need to know about boosting it safely.

Normal testosterone range in men: 300–1000 ng/dL ·
Testosterone decline per year after age 30: ~1% ·
Normal testosterone range in women: 15–70 ng/dL ·
Percentage of men over 60 with low testosterone: ~20%

Six key facts about testosterone, one pattern: it’s a steroid hormone with distinct production sites and normal ranges that vary by sex.

What is testosterone?

Testosterone production

• Testosterone is a sex hormone produced primarily in the testes in men and ovaries in women (StatPearls (NCBI Bookshelf)).
• A small amount is also made by the adrenal glands in both sexes (StatPearls (NCBI Bookshelf)).

Production is regulated by the hypothalamus and pituitary gland through a feedback loop that involves luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

Normal testosterone levels by age and sex

• In men, normal total testosterone ranges from 300 to 1000 ng/dL, with levels peaking in early adulthood and declining gradually after age 30 (StatPearls (NCBI Bookshelf)).
• In women, normal levels are 15–70 ng/dL, produced mainly in the ovaries and adrenal glands (StatPearls (NCBI Bookshelf)).

The pattern: age-related decline is normal, but when levels fall below the threshold and cause symptoms, it becomes a clinical condition called hypogonadism.

The implication: Testosterone’s influence extends far beyond reproduction, affecting nearly every system in the body.

What does testosterone do for a man?

Sexual development and function

• Testosterone drives primary male sexual development, including testicular descent, enlargement of the penis and testes, and spermatogenesis (StatPearls (NCBI Bookshelf)).
• It also supports normal erectile function and libido (StatPearls (NCBI Bookshelf)).

Without adequate testosterone, men typically experience erectile dysfunction, loss of morning erections, and reduced sexual desire — the three most specific symptoms according to the British Society for Sexual Medicine (British Society for Sexual Medicine).

Muscle mass and strength

• Testosterone increases muscle mass and regulates body fat distribution (StatPearls (NCBI Bookshelf)).
• It promotes muscle protein synthesis and hypertrophy, which is why low testosterone is linked to loss of muscle mass and increased body fat (StatPearls (NCBI Bookshelf)).

Bone density

• Testosterone supports bone density and helps prevent osteoporosis (StatPearls (NCBI Bookshelf)).
• Low testosterone is associated with increased fracture risk (StatPearls (NCBI Bookshelf)).

Libido and sexual health

• Testosterone stimulates libido in both men and women (StatPearls (NCBI Bookshelf)).
• It also enhances erythropoiesis, helping explain higher hemoglobin and hematocrit levels in men than women (StatPearls (NCBI Bookshelf)).

Mood and cognitive function

• Testosterone enhances energy levels, supports cognitive function, and improves mood (StatPearls (NCBI Bookshelf)).
• Low testosterone is linked to depression, reduced motivation, poor concentration, and irritability (American Urological Association).

The takeaway: testosterone is a multi-system regulator. When levels drop, the effects are felt across sexual, physical, and mental domains.

What does testosterone do for women?

Testosterone’s role in women’s health

• Women produce small amounts of testosterone in the ovaries and adrenal glands (StatPearls (NCBI Bookshelf)).
• Testosterone contributes to sex drive, bone density, and muscle strength in women (Medical News Today).

Despite the lower levels, testosterone plays a meaningful role in female health. Imbalances — either too high or too low — can cause symptoms such as decreased sex drive, infertility, and irregular menstrual periods (Medical News Today).

Hormone balance and libido

• Global consensus guidance supports testosterone treatment for hypoactive sexual desire disorder (HSDD) in women at physiological premenopausal levels after ruling out other causes (The ObG Project summary of global consensus guidelines).
• Reported benefits include increased satisfying sexual events and improvements in desire, arousal, orgasmic function, and pleasure (The ObG Project summary of global consensus guidelines).

The catch: While testosterone therapy shows promise for specific conditions in women, the evidence base is still evolving.

What are the signs of low testosterone?

Physical symptoms

• Loss of muscle mass and strength, increased body fat, gynecomastia, and decreased endurance (Cleveland Clinic).
• Loss of armpit and pubic hair, shrinking testicles, hot flashes, and low or zero sperm count (Cleveland Clinic).
• Reduced bone density and increased fracture risk (StatPearls (NCBI Bookshelf)).

Sexual symptoms

• Low libido, loss of morning or spontaneous erections, and trouble attaining or maintaining an erection (Cleveland Clinic).
• These are the most specific symptoms of hypogonadism (British Society for Sexual Medicine).

Cognitive and emotional symptoms

• Depressed mood, reduced motivation, poor concentration, memory issues, and irritability (American Urological Association).
• Fatigue, low energy, and diminished work or physical performance (American Urological Association).

The pattern: symptoms develop gradually, and many men attribute them to aging or stress. A blood test is the only way to confirm low testosterone.

What will increase testosterone do?

Benefits of increasing testosterone

• Testosterone therapy can improve libido, muscle mass, bone density, and mood in men with clinically low levels (The Endocrine Society guideline).
• It enhances sexual function, well-being, and energy (The Endocrine Society guideline).

Risks of testosterone therapy

• Potential risks include sleep apnea, acne, breast enlargement (gynecomastia), and possible cardiovascular issues (Mayo Clinic).
• Testosterone therapy may stimulate noncancerous growth of the prostate and growth of existing prostate cancer (Mayo Clinic).
• Long-term cardiovascular risks in older men remain unclear (StatPearls (NCBI Bookshelf)).

Natural ways to increase testosterone

• Lifestyle changes such as resistance exercise, adequate sleep, weight loss, and stress reduction can naturally boost testosterone (Harvard Health).
• A diet rich in protein, healthy fats, and zinc (found in oysters, red meat, and nuts) may support healthy levels (Harvard Health).
• Avoiding excessive alcohol and maintaining a healthy body weight are key (Harvard Health).

How to raise testosterone naturally: steps

1. Lift weights. Resistance training, especially compound lifts like squats and deadlifts, stimulates testosterone production (Harvard Health).
2. Get enough sleep. Aim for 7–9 hours per night; sleep deprivation lowers testosterone (Harvard Health).
3. Manage stress. Chronic stress raises cortisol, which suppresses testosterone (Harvard Health).
4. Eat a balanced diet. Include zinc, vitamin D, and healthy fats from foods like eggs, fatty fish, and nuts (Harvard Health).
5. Maintain a healthy weight. Excess body fat, especially belly fat, is linked to lower testosterone (Harvard Health).
6. Limit alcohol. Heavy drinking can reduce testosterone production (Harvard Health).

Confirmed facts and what’s unclear

What this means: The evidence supports testosterone therapy for specific conditions, but gaps remain, particularly regarding long-term safety and optimal targets.

Testosterone plays multiple important roles in the body, such as development of the penis and testes, deepening of the voice, and it may play a role in balding.

— Harvard Health Publishing

Testosterone is a sex hormone that helps men build muscle and develop sexual traits, like libido and hair growth.

— Cleveland Clinic

Testosterone therapy may stimulate noncancerous growth of the prostate and growth of existing prostate cancer, and can enlarge breasts.

— Mayo Clinic

For the average man in his 40s noticing low energy and a dwindling sex drive, the decision to pursue testosterone therapy is clear: get a blood test first, then work with a doctor to weigh the benefits against the risks. For men with borderline levels, lifestyle changes are the safer first step — or accept that some decline is a normal part of aging.

For those looking to maintain healthy levels, natural ways to boost testosterone can complement the body’s natural production.

Frequently asked questions