Testosterone
Definition
Measures testosterone in the blood. There are three types of test:
| Test | What it measures |
|---|---|
| Total testosterone | Bound + free testosterone. The most commonly used test |
| Free testosterone | Only testosterone that is not bound to protein |
| Bioavailable testosterone | Free testosterone + testosterone bound to proteins other than SHBG |
Most testosterone is bound to proteins and cannot be used immediately by the body.
Purpose
- In men: Symptoms of low testosterone, reduced sex drive, erectile dysfunction, infertility, hair loss, muscle loss, bone thinning
- In women: Suspected high testosterone, abnormal facial/body hair, male-pattern hair loss, deepening of the voice, irregular periods, infertility, acne
Results
A testosterone level test alone cannot diagnose any health condition, but abnormal results together with symptoms may be a sign of a health problem.
- Low in men, testicular problems, liver/kidney disease, pituitary disorders, or genetic conditions such as Klinefelter syndrome
- High in men, testicular tumors or steroid use
- High in women, PCOS, ovarian cancer, adrenal gland disorders or pituitary dysfunction
Normal Values
Laboratory-specific.
Risks and Limitations
Timing is critical: The blood sample is taken between 07:00 and 10:00 in the morning, when testosterone levels are typically at their highest. Levels fluctuate naturally during the day.