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Last updated October 25, 2019. 3 minute read

Sex drive and testosterone: the relationship explained

Testosterone is one of the hormones that physiologically stimulates the male sex drive. Researchers have found that reduced libido is one of the most common symptoms of a low testosterone level (low T).

Self Written by Michael Martin
Reviewed by Dr. Mike Bohl, MD, MPH

Testosterone could use a new publicist. Over the years, it’s become shorthand for some of the less desirable male qualities—aggression, violence, the inexplicable popularity of Nickelback. But the truth is, women have testosterone too. Men with higher testosterone levels aren’t automatically violent. In reality, testosterone is the Martin Sheen, not Charlie Sheen, of hormones. It’s vital and indispensable to several bodily processes. One of these is sex drive.

Vitals

  • Testosterone is an important sex hormone in men and women that affects many and varied bodily processes.
  • Testosterone is one of the hormones that stimulate male and female sex drive.
  • A low testosterone level (“low T”) can cause low libido, along with many other symptoms.
  • Low T can be diagnosed with a blood test (done twice).
  • Testosterone replacement therapy, which comes in several forms, may alleviate symptoms.

What is testosterone?

Testosterone is a sex hormone in both men and women. In men, it’s produced in the testicles in response to signals from the pituitary gland (some is also made in the adrenal glands). Along with DHT (another hormone which is synthesized from testosterone), testosterone is responsible for the physical changes that happen to males at puberty, including secondary sexual characteristics, muscle growth, and sperm production. And it’s important to a ton of bodily processes in both men and women throughout life.

In men, testosterone plays a major role in:

  • Libido
  • Erectile function
  • Sperm production
  • Bone density and muscle mass
  • Red blood cell production
  • Growth of facial and body hair
  • Mood

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Does testosterone increase sex drive?

Testosterone is one of the hormones that physiologically stimulates the male sex drive. How does it do that, exactly? Researchers aren’t sure, but they’ve found that reduced libido is one of the most common symptoms of a low testosterone level (low T).

As part of the Massachusetts Male Aging Study (MMAS), researchers talked to 1,632 men about their sex drive, then measured their testosterone levels (Travison, 2006). The scientists found that the men who reported lower sexual desire had a higher chance of having low T.

Low testosterone and sex

Low testosterone, also known as hypogonadism, is an abnormally low level of testosterone in the blood, measuring less than 300 ng/dL (nanograms per deciliter). A “normal” testosterone level is between 300 and 1,000 ng/dL. According to the Cleveland Clinic, about 40% of men age 45 or older have a low testosterone level. 

Testosterone levels naturally decline with age, beginning around age 30 and continuing to drop about 1% per year. The pituitary gland sends fewer messages telling the testes to make testosterone, and the testes obey. Meanwhile, a protein called sex hormone-binding globulin (SHBG) increases in men as they age. All of this reduces the active (a.k.a. free) form of testosterone in the body. 

Because T affects so many bodily systems, low levels can have several seemingly unrelated symptoms, including fatigue, loss of muscle mass, increased body fat, and anemia (low red blood cell count).

In terms of sexual health, low testosterone can cause

  • Low libido
  • Erectile dysfunction with loss of morning erections 
  • Reduced sperm count
  • Infertility

In men with low testosterone, their symptoms can be resolved with testosterone replacement therapy.

Does low testosterone cause ED?

It can. But in most cases, ED is caused by other factors. If your testosterone level isn’t low, taking testosterone therapy likely won’t cure your ED. Read everything you need to know about erectile dysfunction here.

A healthcare provider can measure your testosterone level with a blood test. T levels are usually highest in the morning and can vary throughout the day. So doctors usually require two early-morning testosterone levels (usually between 7 and 9 a.m.) on different days to be low (< 300 ng/dL) before diagnosing hypogonadism in men. That’s a relatively good sign of a chronic issue.

What is testosterone therapy?

Testosterone replacement therapy (TRT) is an FDA-approved way to increase testosterone and treat the symptoms of low testosterone. Testosterone therapy can be administered in these ways:

  • Skin patch
  • Gels
  • Injections
  • Surgically implanted pellets
  • Tablets

A common side effect of testosterone replacement therapy is low sperm count. Artificial testosterone can cause your body to slow the production of sex hormones because it thinks you’re making enough. This may have the undesired side effect of slowing down sperm production and worsening your body’s ability to make its own testosterone, which could make you dependent on continued TRT.

According to the American Urological Association, other side effects can include acne, enlarged prostate, enlarged breasts, lower fertility, and worsening sleep apnea. The data is conflicting, but the FDA has concluded that TRT can increase the risk of cardiovascular issues.

If you’re experiencing a chronic low sex drive or reduced sexual function, talk to your healthcare provider. They can evaluate you for other conditions that might be causing your symptoms, refer you to a specialist in endocrinology if appropriate, and prescribe testosterone treatment if it’s right for you.