Free Androgen Index
Also written as: FAI — Free Androgen Index
A calculated ratio of total testosterone to sex hormone-binding globulin, used to estimate bioavailable testosterone levels.
Full Definition
The Free Androgen Index (FAI) is a calculated parameter derived from the ratio of total testosterone to sex hormone-binding globulin (SHBG), multiplied by 100. This index provides an estimate of bioavailable testosterone when direct measurement is not available. It is particularly useful in evaluating hyperandrogenic conditions in women, though it has limitations compared to direct free testosterone measurement. The FAI is commonly included in PCOS workups and hirsutism evaluations.
Usage
Usage note: Often confused with Free Testosterone Index; ensure correct terminology in endocrine reports.
In Context
- "The patient's Free Androgen Index was elevated at 8.5, supporting the diagnosis of hyperandrogenism." — Laboratory report
- "Calculate the FAI using the total testosterone and SHBG values from the morning draw." — Clinical protocol