Testosterone is a hormone that helps with things like muscle growth, bone strength, and even mood. If your testosterone levels are too low, you might feel tired, weak, or have a low sex drive.
Bioavailable testosterone refers to the fraction of testosterone that is freely available for bodily use. It includes free testosterone (unbound) and testosterone that is loosely bound to albumin, a protein in the blood. This form of testosterone is important because it is readily available to tissues and organs, influencing various bodily functions like muscle growth, fat distribution, bone density, libido, and mood regulation.
Bioavailable testosterone is different from total testosterone, which measures all testosterone in the blood, including the majority that is tightly bound to sex hormone-binding globulin (SHBG) and is unavailable for direct use by the body.
The Bioavailable Testosterone blood test measures the amount of testosterone available to your body's cells, free testosterone and testosterone loosely attached to a blood protein called albumin.
Abnormal Bioavailable Testosterone Levels
Low Bioavailable Testosterone - Causes
- Aging: Testosterone levels naturally decline with age, which can reduce bioavailable testosterone.
- Hypogonadism: A condition where the testes or ovaries produce insufficient amounts of testosterone or other sex hormones.
- Obesity: Increased body fat can lead to higher estrogen levels and lower testosterone production.
- Chronic illness: Conditions, such as liver or kidney disease, diabetes, and metabolic syndrome can affect hormone levels.
- Elevated SHBG: High levels of sex hormone-binding globulin reduce the amount of testosterone available for use by the body.
- Medications: Certain drugs, like opioids, glucocorticoids, and antidepressants, can lower testosterone levels.
Low Bioavailable Testosterone - Symptoms
- Fatigue or low-energy
- Reduced libido or sexual dysfunction
- Depression or mood changes
- Loss of muscle mass or strength
- Increased body fat, particularly around the abdomen
- Decreased bone density or osteoporosis
- Difficulty concentrating or memory problems
High Bioavailable Testosterone - Causes
- Anabolic steroid use: Some individuals use anabolic steroids to enhance muscle mass and athletic performance, leading to unnaturally high testosterone levels.
- Polycystic ovary syndrome (PCOS): In women, PCOS can cause elevated levels of bioavailable testosterone, leading to symptoms like irregular menstruation and increased hair growth.
- Adrenal disorders: Overproduction of testosterone due to adrenal gland dysfunction can cause elevated levels.
- Androgen-secreting tumors: Rare tumors of the testes, ovaries, or adrenal glands can increase testosterone production.
High Bioavailable Testosterone - Symptoms in Males
- Aggressiveness or irritability
- Acne or oily skin
- Sleep apnea
- Excessive muscle mass
- Balding or hair thinning
High Bioavailable Testosterone - Symptoms in Females
- Irregular menstrual cycles
- Excessive facial or body hair (hirsutism)
- Deepening of the voice
- Acne
- Male-pattern baldness
.svg){kind=icon}
.svg)