What is Free Androgen Index?
The Free Androgen Index (FAI) is not a direct measurement of a specific substance in your blood. Instead, it's a calculated value that represents the percentage of androgens (like testosterone) in your blood that are not bound to proteins. These unbound androgens are the ones that are biologically active and can readily interact with your body's tissues.
Your body's active hormone pool
Androgens, primarily produced by the testes in men and the ovaries and adrenal glands in women, play vital roles in sexual development, muscle mass, bone density, and mood. When produced, most of these hormones bind to carrier proteins in the bloodstream, mainly Sex Hormone-Binding Globulin (SHBG) and albumin. Only the androgens that remain unbound, or 'free,' are available for your cells to use.
Reflecting available hormonal power
The FAI provides a more accurate picture of androgen availability than measuring total testosterone alone. It helps to understand how much of the total testosterone is actually usable by your body, taking into account the influence of SHBG levels, which can vary significantly among individuals and due to various physiological factors.
Key to hormonal balance
This derived marker is crucial for assessing hormonal balance, particularly in situations where total testosterone levels might appear normal but the amount of free, active hormone is either too high or too low, impacting various bodily functions.
Why is Free Androgen Index important?
The Free Androgen Index offers a refined view of the biologically active androgens available in your body. It helps in understanding the true androgenic status, which is essential for a wide range of physiological processes in both men and women. Measuring this index allows for a more nuanced assessment of hormonal health beyond total hormone levels alone.
When levels drop too low
Low FAI can indicate that a disproportionately large amount of your androgens are bound to proteins, leaving less available for your tissues. This can contribute to symptoms such as decreased libido, fatigue, reduced muscle mass, impaired mood, and slower recovery from exercise. In women, it may be associated with irregular menstrual cycles and reduced fertility.
When levels climb too high
A high FAI suggests that there is an excess of free, active androgens circulating in your bloodstream. In men, this could potentially be linked to symptoms like acne, increased aggression, and hair loss. In women, elevated free androgens are a hallmark of conditions like Polycystic Ovary Syndrome (PCOS), leading to symptoms such as hirsutism (excess hair growth), acne, irregular periods, and fertility issues.
The long view on Free Androgen Index
Maintaining a balanced FAI is important for long-term hormonal equilibrium. Chronically high or low levels can impact metabolic health, cardiovascular well-being, and reproductive function. Understanding and optimizing your FAI can contribute to sustained energy levels, a healthy mood, robust physical function, and overall resilience.
What do my Free Androgen Index results mean?
Low Free Androgen Index levels
A low FAI suggests that while total testosterone may be within a normal range, the amount of readily available, active testosterone is reduced. This can occur when SHBG levels are very high, binding up a large portion of circulating testosterone. Symptoms might include low energy, reduced sex drive, and diminished muscle tone.
Optimal Free Androgen Index levels
Optimal FAI levels indicate a healthy balance where a sufficient amount of androgens are free and biologically active, supporting vital bodily functions without being excessively high. This range supports energy, mood, libido, and muscle health. The precise 'optimal' range can vary based on age, sex, and individual physiology.
High Free Androgen Index levels
A high FAI signifies an abundance of free, active androgens. This can be indicative of underlying hormonal imbalances. In women, it's often associated with conditions like PCOS. In men, very high levels might contribute to androgenic side effects, although this is less common and usually seen with exogenous androgen use.
Factors that influence Free Androgen Index results
Several factors can influence FAI calculations, including the measured levels of total testosterone and SHBG. Conditions like liver disease, thyroid disorders, obesity, aging, and certain medications can significantly alter SHBG levels, thereby impacting the FAI. Pregnancy also affects hormone binding proteins.
Do I need a Free Androgen Index test?
Experiencing persistent fatigue, unexplained changes in mood, decreased libido, or concerns about hair growth or menstrual irregularities? These symptoms can sometimes be linked to imbalances in your active hormone levels, and understanding your Free Androgen Index could provide valuable insights.
The Free Androgen Index is a calculated marker that reveals the proportion of your testosterone that is biologically active and available for your body to use. By assessing this index, we can gain a clearer picture of your hormonal status, going beyond just total hormone levels to understand how your body is truly utilizing these key hormones.
Testing your Free Androgen Index empowers you to take a proactive approach to your health. It provides objective data that can help personalize your wellness strategy, guiding targeted interventions to optimize your hormonal balance, alleviate symptoms, and enhance your overall vitality and long-term well-being.
Technical & PDF Reading Details
Measurement context
BioMedli calculates this only when all required source measurements are present on the same test date and their units can be normalized safely. Formula: (total testosterone nmol/L / SHBG nmol/L) * 100.
How PDF reading works
Read directly when printed. Otherwise calculate from valid same-date source values and retain calculation provenance.
Calculation
(total testosterone nmol/L / SHBG nmol/L) * 100
Required same-date inputs
- Testosterone, Total
- Sex Hormone Binding Globulin (SHBG)