Free Androgen Index
Free Androgen Index
Free androgen index (FAI) measures the proportion of unbound "free" testosterone in blood and is used to help diagnose androgen disorders.
Free androgen index (FAI) measures the proportion of unbound "free" testosterone in blood and is used to help diagnose androgen disorders.
Free Androgen Index
Normal range
Normal range
Male: 35-92 Female: 0-6
Male: 35-92 Female: 0-6
Normal range
Male: 35-92 Female: 0-6
Male: 35-92 Female: 0-6
Normal range
Free Androgen Index
Free Androgen Index
Free androgen index (FAI) measures the proportion of unbound "free" testosterone in blood and is used to help diagnose androgen disorders.
Free Androgen Index
Normal range
Male: 35-92 Female: 0-6
Normal range
Male: 35-92 Female: 0-6
Male: 35-92 Female: 0-6
Normal range
Free Androgen Index
Free Androgen Index
Free androgen index (FAI) measures the proportion of unbound "free" testosterone in blood and is used to help diagnose androgen disorders.
Free Androgen Index
Normal range
Male: 35-92 Female: 0-6
Normal range
Male: 35-92 Female: 0-6
Male: 35-92 Female: 0-6
Normal range
Free Androgen Index
Dr. Thiviya Sivakanthan
MBBS
Your Body's Hormone Activity Scorecard
Your Body's Hormone Activity Scorecard
Every day, your body performs a complex calculation that determines how much active testosterone is actually available to your cells—the Free Androgen Index (FAI). When this calculation reveals imbalances, it can explain mysterious symptoms like unexpected hair growth, stubborn acne, irregular periods, or fertility problems that seem to have no clear cause, often providing the missing piece of your hormonal puzzle.
The Free Androgen Index is like your body's hormone activity scorecard, revealing the true testosterone story by comparing your total testosterone to the protein that controls it. Think of it as nature's way of showing you what's really happening with your androgens—when your FAI is balanced, your hormones work harmoniously, but when it's disrupted, even normal testosterone levels can cause significant problems.
Every day, your body performs a complex calculation that determines how much active testosterone is actually available to your cells—the Free Androgen Index (FAI). When this calculation reveals imbalances, it can explain mysterious symptoms like unexpected hair growth, stubborn acne, irregular periods, or fertility problems that seem to have no clear cause, often providing the missing piece of your hormonal puzzle.
The Free Androgen Index is like your body's hormone activity scorecard, revealing the true testosterone story by comparing your total testosterone to the protein that controls it. Think of it as nature's way of showing you what's really happening with your androgens—when your FAI is balanced, your hormones work harmoniously, but when it's disrupted, even normal testosterone levels can cause significant problems.
How FAI Reveals Your True Androgen Status
How FAI Reveals Your True Androgen Status
How FAI Reveals Your True Androgen Status
Discover why this calculated measurement often explains symptoms that total testosterone levels miss entirely.
What Drives Your FAI Up or Down
What Drives Your FAI Up or Down
What Drives Your FAI Up or Down
From insulin resistance to weight changes, understand the factors that can dramatically alter your androgen activity.
How FAI Reveals Your True Androgen Status
The Hormone Availability Calculator: Your Free Androgen Index is a calculation that determines how much testosterone is actually available for use in your body. It's calculated by dividing your total testosterone by your SHBG (Sex Hormone Binding Globulin) and multiplying by 100, creating a percentage that reveals your true androgen activity level.
This calculation is crucial because you might have normal total testosterone levels but still experience symptoms of androgen excess or deficiency. It's like having a bank account with a good balance but limited access to your funds—the FAI tells you how much you can actually spend, not just how much you have.
The Missing Piece of the Puzzle: Many women with PCOS, unexplained hair growth, or persistent acne have normal testosterone levels but elevated FAI scores. This explains why their symptoms persist despite apparently normal hormone tests. The FAI acts like a detective, revealing the true culprit behind androgen-related symptoms when other tests appear normal.
Gender-Specific Significance: In women, the FAI is particularly important because even small increases in available testosterone can cause significant symptoms. Your body is designed to be extremely sensitive to androgens, so a slightly elevated FAI can trigger masculine features, irregular periods, or fertility problems that seem disproportionate to your actual testosterone levels.
How FAI Reveals Your True Androgen Status
The Hormone Availability Calculator: Your Free Androgen Index is a calculation that determines how much testosterone is actually available for use in your body. It's calculated by dividing your total testosterone by your SHBG (Sex Hormone Binding Globulin) and multiplying by 100, creating a percentage that reveals your true androgen activity level.
This calculation is crucial because you might have normal total testosterone levels but still experience symptoms of androgen excess or deficiency. It's like having a bank account with a good balance but limited access to your funds—the FAI tells you how much you can actually spend, not just how much you have.
The Missing Piece of the Puzzle: Many women with PCOS, unexplained hair growth, or persistent acne have normal testosterone levels but elevated FAI scores. This explains why their symptoms persist despite apparently normal hormone tests. The FAI acts like a detective, revealing the true culprit behind androgen-related symptoms when other tests appear normal.
Gender-Specific Significance: In women, the FAI is particularly important because even small increases in available testosterone can cause significant symptoms. Your body is designed to be extremely sensitive to androgens, so a slightly elevated FAI can trigger masculine features, irregular periods, or fertility problems that seem disproportionate to your actual testosterone levels.
How FAI Reveals Your True Androgen Status
The Hormone Availability Calculator: Your Free Androgen Index is a calculation that determines how much testosterone is actually available for use in your body. It's calculated by dividing your total testosterone by your SHBG (Sex Hormone Binding Globulin) and multiplying by 100, creating a percentage that reveals your true androgen activity level.
This calculation is crucial because you might have normal total testosterone levels but still experience symptoms of androgen excess or deficiency. It's like having a bank account with a good balance but limited access to your funds—the FAI tells you how much you can actually spend, not just how much you have.
The Missing Piece of the Puzzle: Many women with PCOS, unexplained hair growth, or persistent acne have normal testosterone levels but elevated FAI scores. This explains why their symptoms persist despite apparently normal hormone tests. The FAI acts like a detective, revealing the true culprit behind androgen-related symptoms when other tests appear normal.
Gender-Specific Significance: In women, the FAI is particularly important because even small increases in available testosterone can cause significant symptoms. Your body is designed to be extremely sensitive to androgens, so a slightly elevated FAI can trigger masculine features, irregular periods, or fertility problems that seem disproportionate to your actual testosterone levels.
High FAI and Androgen Excess
Physical Manifestations: High FAI in women acts like an internal masculinising force, causing symptoms that can significantly impact your confidence and quality of life. You might notice increased facial or body hair growth, particularly on your chin, upper lip, or chest. Your scalp hair might thin in a male pattern, starting at the temples or crown, whilst acne becomes more persistent and difficult to treat.
These changes aren't just cosmetic concerns—they're your body's way of signalling that too much active testosterone is circulating through your system. It's like having a hormone amplifier turned up too high, causing effects that feel alien to your natural feminine state.
Metabolic Consequences: High FAI often indicates underlying metabolic problems that extend far beyond appearance. Women with elevated FAI frequently struggle with insulin resistance, weight gain around the midsection, and difficulty losing weight despite proper diet and exercise. It's your body's way of showing that your hormone and metabolic systems are interconnected and both need attention.
Reproductive Impact: Elevated FAI can disrupt your menstrual cycle like a hormone hijacker, causing irregular periods, absent ovulation, or fertility problems. Your ovaries may develop multiple small cysts, and you might experience difficulty conceiving even if you're ovulating regularly. The excess androgen activity interferes with the delicate hormone balance needed for normal reproductive function.
Long-term Health Risks: Persistently high FAI isn't just about immediate symptoms—it can increase your risk of developing type 2 diabetes, cardiovascular disease, and metabolic syndrome. It's like having a warning light on your body's dashboard, signalling that important systems need maintenance before more serious problems develop.
High FAI and Androgen Excess
Physical Manifestations: High FAI in women acts like an internal masculinising force, causing symptoms that can significantly impact your confidence and quality of life. You might notice increased facial or body hair growth, particularly on your chin, upper lip, or chest. Your scalp hair might thin in a male pattern, starting at the temples or crown, whilst acne becomes more persistent and difficult to treat.
These changes aren't just cosmetic concerns—they're your body's way of signalling that too much active testosterone is circulating through your system. It's like having a hormone amplifier turned up too high, causing effects that feel alien to your natural feminine state.
Metabolic Consequences: High FAI often indicates underlying metabolic problems that extend far beyond appearance. Women with elevated FAI frequently struggle with insulin resistance, weight gain around the midsection, and difficulty losing weight despite proper diet and exercise. It's your body's way of showing that your hormone and metabolic systems are interconnected and both need attention.
Reproductive Impact: Elevated FAI can disrupt your menstrual cycle like a hormone hijacker, causing irregular periods, absent ovulation, or fertility problems. Your ovaries may develop multiple small cysts, and you might experience difficulty conceiving even if you're ovulating regularly. The excess androgen activity interferes with the delicate hormone balance needed for normal reproductive function.
Long-term Health Risks: Persistently high FAI isn't just about immediate symptoms—it can increase your risk of developing type 2 diabetes, cardiovascular disease, and metabolic syndrome. It's like having a warning light on your body's dashboard, signalling that important systems need maintenance before more serious problems develop.
High FAI and Androgen Excess
Physical Manifestations: High FAI in women acts like an internal masculinising force, causing symptoms that can significantly impact your confidence and quality of life. You might notice increased facial or body hair growth, particularly on your chin, upper lip, or chest. Your scalp hair might thin in a male pattern, starting at the temples or crown, whilst acne becomes more persistent and difficult to treat.
These changes aren't just cosmetic concerns—they're your body's way of signalling that too much active testosterone is circulating through your system. It's like having a hormone amplifier turned up too high, causing effects that feel alien to your natural feminine state.
Metabolic Consequences: High FAI often indicates underlying metabolic problems that extend far beyond appearance. Women with elevated FAI frequently struggle with insulin resistance, weight gain around the midsection, and difficulty losing weight despite proper diet and exercise. It's your body's way of showing that your hormone and metabolic systems are interconnected and both need attention.
Reproductive Impact: Elevated FAI can disrupt your menstrual cycle like a hormone hijacker, causing irregular periods, absent ovulation, or fertility problems. Your ovaries may develop multiple small cysts, and you might experience difficulty conceiving even if you're ovulating regularly. The excess androgen activity interferes with the delicate hormone balance needed for normal reproductive function.
Long-term Health Risks: Persistently high FAI isn't just about immediate symptoms—it can increase your risk of developing type 2 diabetes, cardiovascular disease, and metabolic syndrome. It's like having a warning light on your body's dashboard, signalling that important systems need maintenance before more serious problems develop.
What Drives Your FAI Up or Down
Insulin Resistance: Insulin resistance acts like a powerful FAI booster, simultaneously increasing testosterone production and decreasing SHBG levels. When your cells become resistant to insulin, your ovaries respond by producing more testosterone, whilst your liver produces less SHBG to bind it. This double effect dramatically increases your FAI, like pressing both the accelerator and removing the brakes on androgen activity.
Body Weight and Composition: Excess body fat, particularly around your midsection, can drive up your FAI through multiple mechanisms. Fat tissue produces substances that suppress SHBG production whilst also affecting insulin sensitivity. It's like having a hormone-disrupting factory operating in your body, constantly working to increase your androgen activity levels.
PCOS and Ovarian Function: PCOS acts like a FAI amplification system, causing your ovaries to produce excess testosterone whilst simultaneously reducing SHBG through associated insulin resistance. This condition creates the perfect storm for elevated FAI levels, explaining why women with PCOS often experience severe androgen-related symptoms even when their testosterone levels appear only mildly elevated.
Thyroid Function: Your thyroid works like a master regulator of SHBG production, and thyroid problems can significantly affect your FAI. Hypothyroidism (underactive thyroid) reduces SHBG production, increasing your FAI even without changes in testosterone levels. It's like having a malfunctioning control system that can't properly manage your hormone transport mechanisms.
Medications and Treatments: Certain medications can dramatically affect your FAI by altering either testosterone production or SHBG levels. Birth control pills typically increase SHBG and lower FAI, whilst some other medications can have the opposite effect. Understanding these influences is crucial for interpreting your results accurately.
What Drives Your FAI Up or Down
Insulin Resistance: Insulin resistance acts like a powerful FAI booster, simultaneously increasing testosterone production and decreasing SHBG levels. When your cells become resistant to insulin, your ovaries respond by producing more testosterone, whilst your liver produces less SHBG to bind it. This double effect dramatically increases your FAI, like pressing both the accelerator and removing the brakes on androgen activity.
Body Weight and Composition: Excess body fat, particularly around your midsection, can drive up your FAI through multiple mechanisms. Fat tissue produces substances that suppress SHBG production whilst also affecting insulin sensitivity. It's like having a hormone-disrupting factory operating in your body, constantly working to increase your androgen activity levels.
PCOS and Ovarian Function: PCOS acts like a FAI amplification system, causing your ovaries to produce excess testosterone whilst simultaneously reducing SHBG through associated insulin resistance. This condition creates the perfect storm for elevated FAI levels, explaining why women with PCOS often experience severe androgen-related symptoms even when their testosterone levels appear only mildly elevated.
Thyroid Function: Your thyroid works like a master regulator of SHBG production, and thyroid problems can significantly affect your FAI. Hypothyroidism (underactive thyroid) reduces SHBG production, increasing your FAI even without changes in testosterone levels. It's like having a malfunctioning control system that can't properly manage your hormone transport mechanisms.
Medications and Treatments: Certain medications can dramatically affect your FAI by altering either testosterone production or SHBG levels. Birth control pills typically increase SHBG and lower FAI, whilst some other medications can have the opposite effect. Understanding these influences is crucial for interpreting your results accurately.
What Drives Your FAI Up or Down
Insulin Resistance: Insulin resistance acts like a powerful FAI booster, simultaneously increasing testosterone production and decreasing SHBG levels. When your cells become resistant to insulin, your ovaries respond by producing more testosterone, whilst your liver produces less SHBG to bind it. This double effect dramatically increases your FAI, like pressing both the accelerator and removing the brakes on androgen activity.
Body Weight and Composition: Excess body fat, particularly around your midsection, can drive up your FAI through multiple mechanisms. Fat tissue produces substances that suppress SHBG production whilst also affecting insulin sensitivity. It's like having a hormone-disrupting factory operating in your body, constantly working to increase your androgen activity levels.
PCOS and Ovarian Function: PCOS acts like a FAI amplification system, causing your ovaries to produce excess testosterone whilst simultaneously reducing SHBG through associated insulin resistance. This condition creates the perfect storm for elevated FAI levels, explaining why women with PCOS often experience severe androgen-related symptoms even when their testosterone levels appear only mildly elevated.
Thyroid Function: Your thyroid works like a master regulator of SHBG production, and thyroid problems can significantly affect your FAI. Hypothyroidism (underactive thyroid) reduces SHBG production, increasing your FAI even without changes in testosterone levels. It's like having a malfunctioning control system that can't properly manage your hormone transport mechanisms.
Medications and Treatments: Certain medications can dramatically affect your FAI by altering either testosterone production or SHBG levels. Birth control pills typically increase SHBG and lower FAI, whilst some other medications can have the opposite effect. Understanding these influences is crucial for interpreting your results accurately.
Understanding Your Results
FAI levels vary significantly between men and women, reflecting natural differences in androgen activity. Understanding these ranges helps you know whether your hormone activity is appropriate:
Men's FAI ranges:
Normal: 35-92
Women's FAI ranges:
Normal: 0-6
These ranges are like different speed limits for different types of roads—what's normal depends entirely on your biological context. Women's bodies are designed to be highly sensitive to androgen activity, whilst men naturally operate at much higher levels.
Tracking Treatment Progress: Your FAI can serve as an excellent marker for tracking treatment effectiveness. As treatments for PCOS, insulin resistance, or weight management take effect, you should see your FAI levels gradually decrease alongside improvement in your symptoms. It's like having a scorecard that shows whether your interventions are actually working.
Context Matters: Your doctor will interpret your FAI alongside your symptoms, other hormone levels, and clinical presentation. A slightly elevated FAI with no symptoms might be less concerning than a borderline level with significant androgen excess signs. The number is important, but your overall picture matters more.
Understanding Your Results
FAI levels vary significantly between men and women, reflecting natural differences in androgen activity. Understanding these ranges helps you know whether your hormone activity is appropriate:
Men's FAI ranges:
Normal: 35-92
Women's FAI ranges:
Normal: 0-6
These ranges are like different speed limits for different types of roads—what's normal depends entirely on your biological context. Women's bodies are designed to be highly sensitive to androgen activity, whilst men naturally operate at much higher levels.
Tracking Treatment Progress: Your FAI can serve as an excellent marker for tracking treatment effectiveness. As treatments for PCOS, insulin resistance, or weight management take effect, you should see your FAI levels gradually decrease alongside improvement in your symptoms. It's like having a scorecard that shows whether your interventions are actually working.
Context Matters: Your doctor will interpret your FAI alongside your symptoms, other hormone levels, and clinical presentation. A slightly elevated FAI with no symptoms might be less concerning than a borderline level with significant androgen excess signs. The number is important, but your overall picture matters more.
Understanding Your Results
FAI levels vary significantly between men and women, reflecting natural differences in androgen activity. Understanding these ranges helps you know whether your hormone activity is appropriate:
Men's FAI ranges:
Normal: 35-92
Women's FAI ranges:
Normal: 0-6
These ranges are like different speed limits for different types of roads—what's normal depends entirely on your biological context. Women's bodies are designed to be highly sensitive to androgen activity, whilst men naturally operate at much higher levels.
Tracking Treatment Progress: Your FAI can serve as an excellent marker for tracking treatment effectiveness. As treatments for PCOS, insulin resistance, or weight management take effect, you should see your FAI levels gradually decrease alongside improvement in your symptoms. It's like having a scorecard that shows whether your interventions are actually working.
Context Matters: Your doctor will interpret your FAI alongside your symptoms, other hormone levels, and clinical presentation. A slightly elevated FAI with no symptoms might be less concerning than a borderline level with significant androgen excess signs. The number is important, but your overall picture matters more.
The Takeaway
Your Free Androgen Index provides crucial insights into your true androgen activity levels, often explaining symptoms that other hormone tests miss. This calculated measurement can reveal why you're experiencing unwanted hair growth, acne, or irregular periods even when your testosterone levels appear normal.
If you're struggling with symptoms of androgen excess, irregular periods, or fertility problems that don't seem to match your hormone test results, your FAI could be providing the missing explanation. These aren't just cosmetic concerns—they're your body's way of signalling that your androgen activity needs attention.
A simple calculation using your existing hormone test results can reveal whether your FAI is supporting your health or driving unwanted symptoms. Don't ignore persistent androgen-related symptoms or assume they're just part of your genetic makeup. Understanding your FAI can give you the clarity you need to address the root cause of your hormonal concerns and reclaim control over your body.
The Takeaway
Your Free Androgen Index provides crucial insights into your true androgen activity levels, often explaining symptoms that other hormone tests miss. This calculated measurement can reveal why you're experiencing unwanted hair growth, acne, or irregular periods even when your testosterone levels appear normal.
If you're struggling with symptoms of androgen excess, irregular periods, or fertility problems that don't seem to match your hormone test results, your FAI could be providing the missing explanation. These aren't just cosmetic concerns—they're your body's way of signalling that your androgen activity needs attention.
A simple calculation using your existing hormone test results can reveal whether your FAI is supporting your health or driving unwanted symptoms. Don't ignore persistent androgen-related symptoms or assume they're just part of your genetic makeup. Understanding your FAI can give you the clarity you need to address the root cause of your hormonal concerns and reclaim control over your body.
The Takeaway
Your Free Androgen Index provides crucial insights into your true androgen activity levels, often explaining symptoms that other hormone tests miss. This calculated measurement can reveal why you're experiencing unwanted hair growth, acne, or irregular periods even when your testosterone levels appear normal.
If you're struggling with symptoms of androgen excess, irregular periods, or fertility problems that don't seem to match your hormone test results, your FAI could be providing the missing explanation. These aren't just cosmetic concerns—they're your body's way of signalling that your androgen activity needs attention.
A simple calculation using your existing hormone test results can reveal whether your FAI is supporting your health or driving unwanted symptoms. Don't ignore persistent androgen-related symptoms or assume they're just part of your genetic makeup. Understanding your FAI can give you the clarity you need to address the root cause of your hormonal concerns and reclaim control over your body.
References
British Society for Gynaecological Endoscopy. (2020). Free androgen index in PCOS diagnosis. BJOG Clinical Guidelines.
National Institute for Health and Care Excellence. (2019). Polycystic ovary syndrome: assessment and management. NICE Clinical Guideline.
Royal College of Obstetricians and Gynaecologists. (2021). Androgen excess in women: diagnosis and treatment. RCOG Practice Guidelines.
References
British Society for Gynaecological Endoscopy. (2020). Free androgen index in PCOS diagnosis. BJOG Clinical Guidelines.
National Institute for Health and Care Excellence. (2019). Polycystic ovary syndrome: assessment and management. NICE Clinical Guideline.
Royal College of Obstetricians and Gynaecologists. (2021). Androgen excess in women: diagnosis and treatment. RCOG Practice Guidelines.
References
British Society for Gynaecological Endoscopy. (2020). Free androgen index in PCOS diagnosis. BJOG Clinical Guidelines.
National Institute for Health and Care Excellence. (2019). Polycystic ovary syndrome: assessment and management. NICE Clinical Guideline.
Royal College of Obstetricians and Gynaecologists. (2021). Androgen excess in women: diagnosis and treatment. RCOG Practice Guidelines.
Research articles
Research articles
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