Bioavailable Testosterone

Bioavailable testosterone is the portion of testosterone available to enter cells and have biological effects, impacting muscle, bone, sexual health, and mood in both males and females.

📋 About This Biomarker

Bioavailable testosterone refers to the portion of testosterone in the blood that is either free (unbound) or weakly bound to albumin. Unlike testosterone that is tightly bound to sex hormone-binding globulin (SHBG), bioavailable testosterone can easily enter cells and influence various physiological functions. Testosterone plays a pivotal role in reproductive and sexual health, but it also impacts muscle mass, bone density, fat distribution, mood, and energy levels in both males and females. For males, testosterone is vital for the development of male characteristics and sperm production. In females, while levels are much lower, testosterone supports bone strength, libido, and overall well-being.

🎯 Why We Test This

Testing bioavailable testosterone is important for diagnosing hormone imbalances that affect reproductive health, sexual function, energy levels, and overall well-being. Monitoring levels helps identify issues like testosterone deficiency in men or excess testosterone in women, which may contribute to conditions like PCOS. Regular testing ensures hormone levels are managed appropriately through lifestyle changes or medical interventions.

⚠️ What Affects It

Several factors influence bioavailable testosterone levels, including age, sex, and overall health. As males age, testosterone production naturally declines, often leading to lower bioavailable testosterone. SHBG levels also increase with age, reducing the amount of free testosterone. In females, changes such as pregnancy, menopause, and oral contraceptive use can affect testosterone availability. Conditions like obesity, insulin resistance, and chronic illnesses (e.g., liver disease, kidney disease) can alter testosterone levels. Lifestyle factors such as stress, sleep, physical activity, and diet also play a role.

📈 How to Improve

To lower elevated bioavailable testosterone, managing stress, improving diet, and increasing physical activity can help regulate hormone levels. For women with high testosterone (e.g., due to PCOS), weight management and insulin regulation can help. If levels are low or nearing the low range, hormone replacement therapy (HRT) or testosterone supplementation may be considered, alongside lifestyle changes like improving sleep and reducing stress. For those in the lower range, maintaining physical activity and addressing underlying health issues like obesity or insulin resistance can prevent further declines.

📊 Understanding Your Results (nmol/L)

Low
Low bioavailable testosterone can result in significant symptoms such as erectile dysfunction, loss of muscle mass, fatigue, and depression in males. In females, low testosterone levels may contribute to osteoporosis, low libido, and mood disturbances. Causes may include age-related declines, chronic illness, or conditions such as hypogonadism (in males). For both sexes, addressing underlying health issues and considering medical treatments, such as testosterone replacement therapy (TRT), may be recommended to restore healthy levels.
Optimal
Bioavailable testosterone within the reference range suggests healthy hormonal function. In males, this typically points to a good balance between testosterone production and SHBG levels, supporting sexual health, muscle maintenance, and mood regulation. In females, a balanced level aids in maintaining bone health, libido, and overall energy. Regular monitoring ensures that levels remain optimal, especially as people age or encounter life changes like menopause or andropause. If bioavailable testosterone is nearing the upper limit of the reference range, it could indicate a heightened state of testosterone activity without crossing into abnormal levels. In males, this might be the result of active supplementation or unusually high natural production, while in females, it could signal early signs of conditions like PCOS. It’s essential to monitor symptoms and potentially reassess lifestyle factors like diet and exercise that might influence hormone balance. When bioavailable testosterone approaches the lower limit of the reference range, it might suggest early stages of testosterone deficiency. In males, this can manifest as fatigue, reduced libido, and difficulty building muscle. For females, it might lead to reduced energy, low mood, and decreased sexual desire. Addressing lifestyle factors like stress management, improving sleep, and considering hormone replacement therapy (HRT) or testosterone therapy can help restore balance.
High
Elevated bioavailable testosterone levels in males can indicate conditions such as testosterone supplementation, anabolic steroid use, or less commonly, adrenal or testicular tumours. In females, high levels may be associated with polycystic ovary syndrome (PCOS), a condition where hormone imbalances affect menstrual cycles and fertility. Signs in females might include increased body hair (hirsutism), acne, and irregular menstrual cycles. Addressing the underlying cause is crucial, as sustained high testosterone can lead to more severe health issues.
Also known as: BT, bioav.testo, bioav.testo.