Low Testosterone (Low T) in Men

What is low testosterone?

Testosterone is made mainly in the testicles, under the control of two hormones from the pituitary gland: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). It drives sex drive, erections, sperm production, muscle and bone strength, red blood cell production, body hair and energy.

Levels peak in the late teens and twenties and fall slowly, about 1% a year after 40. Many older men stay within the normal range. Low testosterone with symptoms is called testosterone deficiency or hypogonadism.

Symptoms of low testosterone

Sexual symptoms (the most specific)

• Low libido, meaning reduced interest in sex
• Erectile dysfunction and fewer spontaneous morning erections
• Reduced semen volume and infertility

Physical symptoms

• Fatigue and reduced energy
• Loss of muscle mass and strength, more belly fat
• Breast tenderness or enlargement (gynecomastia)
• Less body and facial hair, smaller or softer testicles
• Hot flashes and sweats, especially when levels drop sharply
• Thinning bones (osteoporosis) and fractures
• Mild anemia

Mood and thinking

• Low mood, irritability and poor motivation
• Poor concentration
• Sleep problems

Many of these symptoms have other causes, such as depression, thyroid disease, sleep apnea or simply poor sleep. That is why blood tests are essential before treatment.

Normal testosterone levels

Testosterone peaks in the morning, so tests should be drawn between 7 and 10 a.m., ideally fasting, and repeated to confirm a low result. Levels fall temporarily during acute illness, after poor sleep and with heavy exercise training.

Causes of low testosterone

Primary hypogonadism (a testicular problem)

LH and FSH are high because the pituitary is trying to push the failing testicles.

• Klinefelter syndrome (an extra X chromosome), the most common genetic cause
• Undescended testicles, testicular injury or torsion
• Mumps orchitis
• Chemotherapy or radiation
• Hemochromatosis (iron overload)

Secondary hypogonadism (a brain problem)

LH and FSH are low or normal.

• Pituitary tumors, including prolactinoma, which raises prolactin and blocks testosterone
• Obesity and type 2 diabetes, very common causes in middle age
• Opioid painkillers and long-term steroids
• Previous anabolic steroid use, which shuts down natural production for months or longer
• Sleep apnea
• Serious illness, very low body weight or extreme exercise
• Head injury or brain radiation

Low testosterone in young men

In men under 40, look especially for anabolic steroid use, Klinefelter syndrome, pituitary disorders, opioid use, testicular injury and obesity. Low testosterone at a young age usually warrants checks of LH, FSH and prolactin, and sometimes a pituitary MRI.

How low testosterone is diagnosed

1. A history of symptoms, medicines (opioids, steroids), past steroid use and fertility plans.
2. An examination of testicle size, body hair, breast tissue and body weight.
3. Two early-morning total testosterone tests on separate days.
4. LH, FSH and prolactin to find the cause.
5. A complete blood count, and PSA in men over 40 before treatment.
6. Further tests as needed: iron studies, karyotype for Klinefelter syndrome, pituitary MRI, semen analysis, bone density scan.

Treatment

Treat the cause first

• Weight loss of 5 to 10% can raise testosterone meaningfully in men with obesity.
• Treat sleep apnea.
• Review and reduce opioids where possible.
• Treat a prolactinoma with medicine.

Testosterone replacement therapy (TRT)

TRT is offered to men with consistently low levels and clear symptoms. Forms include:

• Gels applied to the skin daily
• Injections every 1 to 2 weeks (short-acting) or every 10 weeks (long-acting)
• Patches, pellets under the skin, nasal gel and oral capsules

Benefits: better sex drive, some improvement in erections, energy and mood, more muscle and less fat, and improved bone density and anemia. Sex drive typically improves within 3 to 6 weeks, while bone benefits take 6 months or more.

Risks and monitoring:

• Raised red blood cell count (hematocrit), which thickens the blood
• Acne, oily skin, breast swelling and ankle swelling
• Worsening of untreated sleep apnea
• Reduced sperm production and infertility, sometimes long-lasting
• Gel transfer to women and children by skin contact
• A large 2023 trial (TRAVERSE) found no increase in major heart events in men with deficiency and heart risk, though some increase in atrial fibrillation and clots was seen

Doctors check testosterone, hematocrit and PSA at about 3 to 6 months, then yearly.

If you want children

Testosterone therapy suppresses sperm production. Men who want to conceive are usually treated instead with medicines that stimulate the body's own production, such as hCG injections or clomiphene, under a specialist.

Who should not take testosterone

• Men trying to conceive
• Men with prostate or breast cancer
• Men with a high hematocrit
• Men with a heart attack or stroke in the past 3 to 6 months
• Men with normal levels who want a boost for energy, muscle or aging, where benefits are not proven

Frequently asked questions

What are the first signs of low testosterone?

The most specific early signs are a falling sex drive and fewer morning erections. Many men also notice fatigue, low mood, less stamina and difficulty building muscle. Because these overlap with stress, poor sleep and depression, the diagnosis needs two morning blood tests.

What is a normal testosterone level for a man?

Most labs give a normal adult male range of roughly 300 to 1,000 ng/dL (10.4 to 34.7 nmol/L). The American Urological Association uses 300 ng/dL as a reasonable cutoff for low testosterone. Tests should be done in the morning and repeated to confirm a low result.

Can low testosterone be reversed naturally?

Sometimes. Losing excess weight, treating sleep apnea, exercising, sleeping enough, limiting alcohol and stopping opioids or anabolic steroids can raise testosterone, especially when obesity or medicines are the cause. Low testosterone from testicular damage, Klinefelter syndrome or pituitary disease usually needs medical treatment.

Does testosterone therapy cause infertility?

Yes, it can. Outside testosterone signals the brain to stop making LH and FSH, which shuts down sperm production. Sperm counts often fall to very low levels within months. Men who want children should tell their doctor, who can use fertility-sparing alternatives such as hCG or clomiphene.

Can young men have low testosterone?

Yes. In younger men the common causes are anabolic steroid use, Klinefelter syndrome, pituitary problems including prolactinoma, testicular injury, opioid use and obesity. A young man with low testosterone needs tests to find the cause, not just replacement therapy.

Is low testosterone dangerous?

Untreated long-term testosterone deficiency can lead to thinning bones and fractures, loss of muscle, anemia, low mood and infertility. It is also linked to type 2 diabetes and heart risk, though partly because those conditions cause low testosterone. Finding and treating the cause matters as much as the hormone level.