Understanding Your Testosterone Levels
Unique testosterone facts series
Understanding Your Testosterone
Hormone levels decline as a part of normal aging, and are the cause of several physiological changes. Low testosterone levels in men are associated with a variety of symptoms including reduced motivation, erectile dysfunction, loss of libido, fatigue, increased cholesterol levels, memory loss, reduced muscle mass, and thyroid dysfunction. Because these symptoms are common, physicians will often include hormone levels as part of routine bloodwork. Read on to learn about the different types of testosterone Injections and understand how to interpret your testosterone levels.
The Different Types of Testosterone
There are two main types of testosterone circulating in the body: free testosterone, testosterone bound to albumin, and testosterone bound to sex hormone-binding globulin (SHBG). Approximately 60–70% of circulating testosterone is tightly bound to SHBG and so is “inactive” because it cannot bind to its cellular receptor to elicit physiological effects. The most physiologically relevant form of testosterone is “bioavailable.” Both free testosterone (free T) and albumin-bound testosterone are considered bioavailable, which means that they are free to activate the androgen receptor and elicit biological effects. Free T and albumin-bound testosterone account for ~2% and 30–40% of the total amount of circulating testosterone, respectively .
Testosterone Assay Results
- Men experiencing fertility problems
- Men with erectile dysfunction or a low sex drive
- Boys undergoing premature puberty
- Women developing typically male features, such as excessive facial and body hair or a deepening of the voice
- Women with irregular menstruation
- Patients with prostate cancer receiving androgen-blocking medications
- Men with osteoporosis
A testosterone test measures the levels of total and free testosterone; the “free” test includes both true free and albumin-bound testosterone. The results can then be used to determine if hormone replacement therapy is required. Tests are usually performed in the morning because testosterone levels are highest first thing between 7 AM and 9 AM. The reference ranges used by Quest Diagnostics, a company that performs these assays for many physicians and hospitals, in men are as follows:
|Total testosterone measurable range||250 to 827 ng/dL|
|Bioavailable testosterone normal range|
|Age 18–69 years||110.0 to 575.0 ng/dL|
|Age >69 years||15.0 to 150.0 ng/dL|
|Free testosterone normal range|
|Age 18–69 years||46.0 to 224.0 pg/mL|
|Age >69 years||
6.0 to 73.0 pg/mL
If your results fall within these ranges they are considered “normal” and any symptoms are likely to be attributable to another condition or hormone. However, reference ranges are only guidelines, and so what is considered normal for one person could be high or low in other people.
What do Low Testosterone Levels Mean?
If your testosterone assay results are low, you do not need to worry. It could be a result of normal aging, due to a medication you are taking, or it could be secondary to the altered production of other hormones such as luteinizing hormone or follicle-stimulating hormone. Your physician will discuss the results with you, try to identify the reason for the low levels, and prescribe any necessary medications.
- Jarari, N., et al., A review on prescribing patterns of antihypertensive drugs. Clin Hypertens, 2015. 22: p. 7.