Free Testosterone Index
Also written as: FTI — Free Testosterone Index
A calculated value estimating free testosterone levels using total testosterone and SHBG measurements.
Full Definition
The free testosterone index (FTI) is a calculated parameter that estimates the amount of biologically active free testosterone by using the ratio of total testosterone to sex hormone-binding globulin (SHBG). The FTI provides an indirect assessment of free testosterone when direct measurement is not available or reliable. While not as accurate as equilibrium dialysis or ultrafiltration methods for measuring free testosterone, the FTI is more practical and cost-effective for routine clinical use, particularly in evaluating hypogonadism and androgen excess disorders.
Usage
Usage note: Clearly distinguish from directly measured free testosterone values.
In Context
- "The free testosterone index was calculated as 45, indicating low bioavailable testosterone." — Andrology report
- "FTI calculation requires both total testosterone and SHBG measurements from the same sample." — Laboratory protocol