Most men are familiar with testosterone, but not all of them are familiar with “free testosterone” and “bound testosterone.”
The majority of testosterone in the body is bound to one of two proteins: sex hormone-binding globulin (SHBG) and albumin. However, a small proportion of testosterone is unattached to either protein. This is what is called free testosterone. Free testosterone and albumin-bound testosterone are easily consumed by the body as the directly bioavailable testosterone resource it possesses.
Total testosterone refers to the total amount of free and bound testosterone in the body.
Testosterone plays a key role in developing the following functions:
- Development of sexual characteristics and sex drive
- Producing and keeping erections firm for sexual activity
- Improved fertility and sperm quality
- Facial and body hair growth
- Mood regulation
- Promoting the growth of muscle and bone mass
- Aiding in the production of red blood cells
Testosterone: Where does it come from?
Testosterone production is a quite complex process similar to most hormonal pathways. Here’s how it works, in a nutshell:
- The hypothalamus, located in the brain, releases GnRH (gonadotropin-releasing hormone).
- GnRH instructs the pituitary gland to introduce luteinizing hormone (LH) into the bloodstream.
- In men, once LH arrives in the testicles through blood flow, it stimulates special cells in the testes called Leydig cells, which are responsible for producing testosterone.
- In women, theca cells, or specialized cells located in the ovaries, produce testosterone.
- As testosterone levels increase in the bloodstream, signals instruct the pituitary gland and the hypothalamus to cease testosterone production.
It’s an intricate process, but this is the general blueprint of how the body tries to regulate hormone levels.
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Why should I test for free testosterone levels?
Many men are conscious of their testosterone levels. Especially more so given the fact that aging diminishes testosterone levels over time, with some studies indicating a decline beginning at age 30 and then declining progressively over time. However, low testosterone isn’t necessarily a medical problem that requires immediate attention.
Some individuals develop symptoms that indicate a testosterone deficiency. Up to 12% of men may have low testosterone. One in two men aged 80 and above, for instance, may have insufficient testosterone.
If you suspect you might have low testosterone levels, consult your doctor and get your levels tested. It’s best to examine both your total and free testosterone levels. Many people check for their total testosterone levels but often forget to test their free testosterone. Free testosterone levels, however, may fall faster than your total testosterone.
Some individuals may register normal overall testosterone levels but may have low free testosterone. Testing only for one and not the other means you may not be getting the full picture of your hormonal health.
Free testosterone is most accurately tested using a process known as equilibrium dialysis, but this test isn’t readily available across providers, besides being time-consuming itself. Thus, many tests rely on indicators that help count free testosterone.
What are normal free testosterone levels?
Most of the time, when people are talking about their testosterone, they refer to their total testosterone levels rather than their “normal” testosterone levels, which can be difficult to ascertain.
The accepted “normal” level of testosterone in the bloodstream runs between 300 to 1000 nanograms per deciliter (ng/dL). This figure varies on a daily basis and by what time of day the test is taken, so healthcare providers tend to test total testosterone levels between 8 to 10 in the morning on two separate occasions. Testosterone levels below 300 ng/dL are considered deficient.
Meanwhile, free testosterone is hard to measure in a direct manner. Laboratories will use an indirect measure of free testosterone as an equation counting your total testosterone and other select values. Normal free testosterone ranges may change based on which lab you use, and different laboratories will have different normal ranges.
In general, free testosterone clocking under 50 to 65 picograms per milliliter (pg/mL) is considered deficient. Such levels are often reviewed in the context of a person having low total testosterone.
What causes low testosterone levels in men?
Certain underlying medical conditions may lead to low testosterone, such as the following:
- Being overweight or obese
- Testicular damage
- Autoimmune diseases
- Diabetes
- A history of undergoing chemotherapy or radiation
- Infections
- Thyroid/pituitary gland dysfunction
- Side effects of certain medications such as antidepressants and narcotics
In such cases, treating the underlying medical conditions may lead to the normalization of hormonal levels, including that of testosterone.
If your doctor detects abnormal testosterone measurements, they may want to put you through additional tests such as luteinizing hormone (LH), or follicle-stimulating hormone (FSH).
What are the effects of low free testosterone levels?
Even when your total testosterone levels are average, you may still experience low free testosterone levels, which may manifest in symptoms of low testosterone such as:
- Reduced sex drive
- Symptoms of erectile dysfunction (ED), including a complete and total loss of erections in the morning
- Loss of lean muscle and bone mass
- Body and facial hair growth
- Frequent feelings of fatigue and weakness
- Anxiety and depression
- Being obese or overweight
- Osteoporosis
- Anemia
Talk to your healthcare provider if you experience any of these symptoms and suspect low testosterone as the primary culprit.
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Is it possible to have excessive levels of testosterone?
Insufficient testosterone levels can lead to a diagnosis of low testosterone. But having extremely high levels of testosterone isn’t good for both men and women, either.
The most prevalent cause of extremely high testosterone levels in men is linked to anabolic or performance-enhancing steroid use in professional athletes. Men with excessive levels of testosterone have reported experiencing symptoms such as:
- Increased prostate cancer risk
- Acne
- The development of breast tissue in men (gynecomastia) as a result of excessive testosterone being converted into estrogen
- Mood swings
- Sleep apnea
- Hypertension or high blood pressure
- High cholesterol levels
- Testicular shrinkage
- Raised red blood cell count
- Testicular or adrenal gland tumors
Women may also experience excessive levels of testosterone. Polycystic ovary syndrome (PCOS) is the leading cause of high testosterone levels in women. PCOS happens when there is an imbalance between female and male hormones, with the latter’s count higher than usual. Women with PCOS generally experience abnormal hair growth, irregular menstrual schedules, problems with fertility, and weight gain, among others.
When should I see a doctor?
Do keep in mind that older men will most likely record lower testosterone levels compared to their younger or middle adulthood –– testosterone decline is a part of aging. However, it’s not about just the numbers when it comes to measuring your testosterone levels –– it’s whether your numbers are causing problems.
The first step to charting your course in these tricky waters is to undergo a complete physical exam with blood tests to check your testosterone levels. From there, your healthcare provider will help you determine the causes of your low T and what treatment approach will work well based on your medical history.
