Low Testosterone in Adult Men and Related Lab Tests

When a male’s body does not produce enough testosterone, the condition is diagnosed as low testosterone, or “low T.” Testosterone is the primary androgen, or sex hormone, for men, and is produced mainly by the testicles. Testosterone maintains male physical characteristics, such as muscle mass and facial hair. It’s also responsible for sex drive, bone health, and overall red blood cell supply. The female body also produces testosterone in significantly smaller quantities. This piece will discuss the issue of low testosterone in adult men.

Testosterone production in the testicles is controlled by the pituitary gland, which is a tiny gland at the base of the brain. There are several reasons for low T, including testicular disease or failure (primary hypogonadism) or a disease or failure of the hypothalamus or pituitary gland (secondary hypogonadism).

Men tend to feel a natural decline in their testosterone level around the age of thirty. This normal stage of aging usually doesn’t cause significant issues. Low T, on its own, is not considered a disease. Low T, by itself, is not an indication that one needs to supplement testosterone with patches or injections. Diagnosing testosterone deficiency in adult males can be done with a combination of clinical evaluation and laboratory testing.

There are numerous factors, aside from aging, that can contribute to low T. Some causes of low T are conditions that men deal with later in their life, such as obesity. Other causes can be related to conditions like Klinefelter syndrome, that individuals are born with, although these conditions are much rarer.

Other things that can cause low testosterone can include:

  • Chronic diseases like HIV, liver disease, Type 2 diabetes, autoimmune diseases, or kidney disease
  • Trauma or injury to the testicles
  • Treating cancer by removing the testicles
  • Radiation or chemotherapy
  • Narcotic pain medications or antidepressants

The symptoms of low T can be treated with hormone replacement therapy. There are, however, risks with this treatment, and it may not be recommended for every man that suffers from low T.

Symptoms of Low T

There are numerous symptoms and signs of low T, that can vary dramatically from one man to another. Some of them are directly related to testosterone levels, like:

  • Reduced hair on the body and face
  • Extremely small testicles
  • Delayed or incomplete sexual development
  • Symptoms that could suggest a testosterone deficiency:
  • Overall low sex drive
  • Erectile dysfunction
  • Lowered number of spontaneous erections
  • Larger breasts
  • Infertility

Some symptoms are less specific, that could be caused by a variety of conditions, such as:

  • Decreased bone mass
  • Decreased lean muscle mass
  • Depressions
  • Mood changes
  • Weakness
  • Fatigue
  • Obesity
  • Irritability
  • Sleep disturbances
  • Poor memory
  • Reduced focus
  • Tests

The process of diagnosing low T starts with listing out a history of the individual’s symptoms, as well as a physical exam. Then, a series of laboratory tests should be scheduled to evaluate testosterone levels. The American Urological Association and The Endocrine Society both recommend utilizing both a clinical exam and laboratory tests to diagnose low T.

It’s important to note that one should not screen for low T in men without existing signs and symptoms. There are extra laboratory tests that can be used to find out the causes of low T, as well as to monitor individuals who are receiving supplemental hormones.

Lab Tests

Testosterone Levels – This is the single most important lab test for determining that testosterone levels are low. Blood should be taken first thing in the morning to help compensate for daily variations. The level should also be sampled on at least two separate days in order to confirm the results. Around thirty percent of men who initially test with low T levels have normal levels when they are retested. Testosterone can also be measured as a method to monitor the success of treatment.

Two-thirds of testosterone circulates in the blood attached to sex hormone binding globulin, and a little less than one-third of it circulates while bound to albumin. Less than four percent of it circulates as free testosterone in the blood. The bio-available fraction of testosterone is composed of the free plus the albumin-bound testosterone, and these can act on target tissues. Often, measuring the total testosterone will provide your medical team with enough information. In some cases, though, if the level of SHBG is not normal, it may be necessary to test for the free or bioavailable testosterone, as it will reflect an existing medical condition far more accurately.

The appropriate ranges for testosterone levels in adult men naturally decrease with age. Although lab test accuracy has gotten significantly better in the last 20-30 years, results can vary from one lab to another due to differences in equipment and techniques. It’s important to use the range provided by the performing laboratory to determine if your results are within a normal range.

It’s worth recognizing that even when men are younger, the range references the center of the population, so a percentage of the population will have a lower testosterone level than the reference number listed. It’s also important to consider whether older men should have their own specific reference range for testosterone, as the current range is based only on the testosterone levels of younger men. To summarize, men should speak with their healthcare provider about what testosterone test results mean.

Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) – FSH is connected to sperm production, LH stimulates testosterone production overall. These tests are often used to help tell the difference between Low T that is caused by a testicular issue and low T that is caused by a problem that began in the hypothalamus or pituitary gland.

If testosterone is low, and LH and FSH levels are high, the source of Low T may originate in the testicles. When FSH and LH are normal or low, it can demonstrate that the source of low T is a pituitary issue. Normal FSH and LH are usually seen with low T related to age.

Prolactin – This is a pituitary hormone. This is what is tested if the pituitary gland could be the reason for low T. High prolactin levels can also indicate pituitary issues like a tumor. High prolactin can interfere with the function of the testicles.

Several tests can be run for men that are going through testosterone therapy to monitor side effects, including:

Hemoglobin – This should be watched for an increase in red blood cells, called polycythemia. This can be a side effect of hormone replacement therapy, which can lead to vascular issues such as blood clots.

Lipid Panel – This helps check for unhealthy lipid levels.

PSA – to check for prostate cancer