Description

The testosterone free/total test is a blood test used to measure the levels of total testosterone and free testosterone in the bloodstream. Testosterone is a sex hormone primarily produced in the testes in men and in the ovaries and adrenal glands in women, although women produce it in much smaller amounts.

Here’s what each component of the test measures:

1. Total testosterone: This measures the total amount of testosterone in the blood, including both bound and unbound forms. Testosterone binds to proteins in the blood, primarily to sex hormone-binding globulin (SHBG) and albumin. Only a small fraction of testosterone (about 1-2%) circulates in the blood in its unbound, or “free,” form.
2. Free testosterone: This measures the amount of testosterone that is not bound to proteins and is therefore available to exert biological effects on target tissues. Free testosterone is considered the biologically active form of the hormone, as it can freely diffuse into cells and bind to androgen receptors to exert its physiological effects.

The testosterone free/total test is useful in assessing various conditions related to testosterone levels, including:

• Hypogonadism: Low testosterone levels, either due to testicular dysfunction (primary hypogonadism) or pituitary/hypothalamic dysfunction (secondary hypogonadism), can result in symptoms such as decreased libido, erectile dysfunction, fatigue, and decreased muscle mass.
• Hypergonadism: Elevated testosterone levels can occur in conditions such as polycystic ovary syndrome (PCOS) in women and androgen-secreting tumors in both men and women. Symptoms may include acne, hirsutism (excessive hair growth), and menstrual irregularities in women, and virilization (masculinization) in both sexes.
• Monitoring testosterone replacement therapy: In men undergoing testosterone replacement therapy for hypogonadism, the free/total testosterone test can help monitor treatment efficacy and ensure that testosterone levels remain within the therapeutic range.

The interpretation of testosterone levels should take into account the individual’s age, sex, clinical symptoms, and other relevant factors. Additionally, interpretation may vary depending on the specific reference ranges used by the laboratory performing the test.