Testosterone: Meaning, Functions, Sexual Health, Testing, and Therapy

During puberty, testosterone may contribute to:

• growth of the penis and testicles;
• deepening of the voice;
• facial and body-hair growth;
• increased muscle development;
• changes in sexual desire;
• sperm production.

Simple examples include:

• Testosterone is produced in bodies of every sex.
• Testosterone levels normally vary by age and time of day.
• Low testosterone cannot be diagnosed from one symptom alone.
• Prescribed testosterone requires medical monitoring.
• Testosterone therapy may reduce fertility but is not reliable contraception.

Testosterone should not be treated as a measure of how masculine, sexually capable, or valuable a person is.

• produce testosterone;
• measure testosterone;
• have low testosterone;
• receive testosterone therapy;
• take prescribed testosterone.

Examples include:

• The laboratory measured his testosterone level.
• Her body naturally produces testosterone.
• They began testosterone under medical supervision.

Do not normally say a testosterone or testosterones. When discussing separate results, use:

• testosterone levels;
• testosterone measurements;
• testosterone test results.

Common Usage Patterns

The term often appears in phrases such as:

• testosterone level;
• low testosterone;
• high testosterone;
• testosterone test;
• testosterone therapy;
• testosterone injection;
• testosterone gel;
• testosterone production.

Androgens are often described as “male hormones,” but this wording is incomplete because all human bodies normally contain and use them.

Testosterone may affect:

• reproductive development;
• sexual desire;
• muscle and bone tissue;
• body-fat distribution;
• hair growth;
• skin oil production;
• red blood cell production;
• mood and energy.

Its effects depend on the amount present, age, genetics, other hormones, health conditions, medications, and how body tissues respond.

In people with ovaries, testosterone is produced in smaller amounts by the ovaries and adrenal glands. Some other androgens may also be converted into testosterone within body tissues.

Testosterone travels through the blood. Much of it is attached to proteins, while a smaller portion circulates as free testosterone.

These may include:

• enlargement of the penis and testicles;
• sperm production;
• deeper voice;
• facial, pubic, and body hair;
• increased muscle mass;
• growth in height;
• stronger body odor;
• acne;
• increased sexual interest.

The timing and degree of these changes vary widely. Developing earlier or later than peers does not automatically indicate a medical problem.

Sexual interest may also be influenced by:

• emotional well-being;
• relationship quality;
• physical health;
• stress;
• sleep;
• medications;
• other hormones;
• sexual orientation and personal preference.

A higher testosterone level does not guarantee stronger desire or better sexual function. A lower level does not prove that a person is uninterested in sex.

However, taking external testosterone may reduce the hormonal signals that stimulate the testicles. This can lower sperm production, shrink the testicles, and reduce fertility.

For this reason, testosterone treatment is not the same as fertility treatment. Someone who may want genetically related children should discuss fertility preservation and treatment alternatives before beginning therapy.

Testing may be considered when someone has symptoms or signs that could relate to unusually low or high androgen levels. Because testosterone levels may change through the day and between tests, an unexpected result may need to be repeated.

The MedlinePlus testosterone overview explains that total testosterone includes hormone attached to blood proteins and that morning testing and repeat measurement may sometimes be used when evaluating a low result.

A laboratory number should be interpreted alongside:

• symptoms;
• age;
• medical history;
• medications;
• time of testing;
• laboratory reference ranges;
• other relevant hormone tests.

One result alone does not diagnose a hormone disorder.

Possible symptoms may include:

• reduced sexual desire;
• fewer spontaneous erections;
• reduced sperm production;
• fatigue;
• reduced muscle mass;
• decreased bone density;
• hot flashes when levels are very low;
• mood or concentration changes.

These symptoms can have many other causes, including stress, depression, medication effects, sleep disorders, thyroid conditions, chronic illness, or relationship difficulties.

A person should not diagnose low testosterone from symptoms alone or use unregulated supplements as a substitute for medical assessment.

• acne or oily skin;
• increased facial or body hair;
• scalp hair loss in genetically susceptible people;
• menstrual changes;
• voice deepening;
• increased red blood cell concentration;
• changes in genital tissue;
• mood or libido changes.

Possible causes vary and may include medication use, ovarian or adrenal conditions, testicular conditions, or differences in androgen sensitivity.

Physical appearance cannot reliably reveal someone’s testosterone level.

Forms may include:

• injections;
• skin gels;
• patches;
• implanted pellets;
• nasal preparations;
• certain oral or buccal medicines.

Treatment choice depends on medical need, availability, cost, preference, fertility plans, and possible side effects.

The Endocrine Society’s transgender health resource describes injections, gels, and patches as common forms of masculinizing testosterone therapy and emphasizes regular follow-up and laboratory monitoring.

• voice deepening;
• increased facial and body hair;
• greater muscle development;
• changes in body-fat distribution;
• increased skin oiliness or acne;
• menstrual suppression;
• genital growth;
• changes in sexual desire;
• possible scalp hair loss.

Some effects, such as voice deepening, facial-hair development, and genital growth, may not fully reverse after treatment stops.

Results vary between individuals. Testosterone cannot guarantee a particular appearance, voice, body shape, or emotional response.

• acne;
• increased red blood cell concentration;
• changes in cholesterol;
• fluid retention;
• worsening sleep apnea;
• reduced sperm production;
• skin reactions;
• transfer of gel to another person through contact;
• changes in blood pressure or other health measurements.

Monitoring may include blood tests, symptom review, blood pressure, and evaluation of individual health risks.

Testosterone should be taken only in the prescribed amount. Nonmedical or excessive use may increase the risk of serious physical and psychological effects.

Taking testosterone during pregnancy is not recommended because it may affect fetal development. Someone using testosterone who thinks they may be pregnant should contact the prescribing clinician promptly rather than changing treatment without medical guidance.

The NHS guidance on testosterone and pregnancy confirms that pregnancy may remain possible during therapy and recommends contraception when pregnancy is not wanted.

A man may naturally have a lower testosterone level. A woman may naturally have a higher level. A transgender man does not need testosterone to be a man, and a transgender woman does not become less of a woman because her body produces testosterone.

Gender identity concerns who a person is. Testosterone is one hormone involved in physical processes.

Anabolic steroids are synthetic substances related to testosterone. They may be prescribed for limited medical purposes but are also used without supervision to increase muscle or athletic performance.

Unsupervised use may cause:

• infertility;
• testicular shrinkage;
• liver or cardiovascular problems;
• mood changes;
• acne;
• hormonal imbalance.

Natural, herbal, or gym-related marketing does not guarantee that a product is safe.

High testosterone makes someone more masculine.
Masculinity is a social and personal identity, not a laboratory measurement.

Testosterone always increases sexual desire.
Sexual desire is affected by many biological, emotional, and relationship factors.

Testosterone therapy guarantees infertility.
It may reduce fertility, but pregnancy or sperm production may still be possible.

Testosterone is birth control.
It does not reliably prevent pregnancy.

One low result proves testosterone deficiency.
Diagnosis usually requires symptoms, medical assessment, and appropriately interpreted testing.

1. Testosterone is an androgen produced naturally in bodies of every sex.
2. Testosterone contributes to sexual development, bone health, muscle tissue, and reproductive function.
3. Can testosterone levels change during the day?
4. Low testosterone cannot be diagnosed from tiredness or reduced desire alone.
5. Prescribed testosterone may be used to treat confirmed hormone deficiency.
6. Testosterone may also be used as part of masculinizing gender-affirming care.
7. External testosterone may reduce sperm production and fertility.
8. Testosterone should not be used as a reliable form of contraception.
9. A person taking testosterone usually needs regular medical monitoring.
10. Testosterone levels do not determine gender identity, masculinity, or personal worth.

The hormone does not independently determine attraction, sexual orientation, consent, masculinity, or sexual performance. People with similar testosterone levels may have very different identities, bodies, and levels of sexual interest.

Accurate sexuality education treats testosterone as one part of a complex hormonal system. Testing and therapy should be individualized, medically supervised, and discussed alongside fertility, contraception, pregnancy possibilities, sexual health, and personal goals.