What is Free Androgen Index (FAI) ?

Does this test have other names?

FAI

What is this test?

A free androgen index (FAI) is a ratio figured out after a blood test for testosterone. It's used to see if you have abnormal androgen levels.

Both men and women make male hormones called androgens, which include testosterone. During puberty, testosterone helps children develop into adults. As you age, levels of this hormone can fall. This causes health problems for both men and women.

A testosterone test is a blood test that measures total testosterone, free testosterone, and a protein called sex-hormone binding globulin (SHBG). A free androgen index measures testosterone in your blood and compares the total amount of testosterone to SHBG in your body.

Why do I need this test?

You may need this test if you show signs of abnormal androgen levels, which differ in women and men.

These hormones aid in the development of sex organs and other gender-linked traits. For example, androgens play a role in making the female hormone estrogen. When a woman makes too many androgen hormones, she may develop extra body hair and facial hair. With too few androgen hormones, a woman may become very tired, lose bone mass, or have little interest in sex.

If you are a woman, you may have this test if you have extra hair on your body or face. It's possible that abnormal hair growth stems from an ovarian tumor or a condition called polycystic ovarian syndrome (PCOS). Among other things, PCOS causes your ovaries to make too much testosterone. Other symptoms of PCOS include obesity, an irregular menstrual cycle, and prediabetes or diabetes.

Testosterone helps boys develop male traits, and makes facial hair in men. If a teen boy isn't developing normally, certain organs might not be making enough of this hormone. Adult men who don't make enough testosterone may feel weak, lose muscle strength and mass, develop breasts, or lose interest in sex.

What other tests might I have along with this test?

You may also need these tests:

• Total testosterone
• Prolactin
• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• Thyroid-stimulating hormone

If you are a woman, you may also get these tests:

• Ferriman-Gallwey scale to measure if you have an abnormal amount of body hair (hirsutism)
• 24-hour determination of urinary free cortisol for Cushing syndrome, a condition that often causes excessive body hair
• Dehydroepiandrosterone sulfate, or DHEA-S, is a marker for an adrenal source of androgens
• 17-alpha-hydroxyprogesterone (17-OHP)
• ACTH stimulation of 17-OHP, if your 17-OHP level is not clearly normal
• Ovarian ultrasound to find out if you have an ovarian tumor
• Adrenal CT scan to check for an adrenal tumor or other abnormalities