. The Free Testosterone Index (FTI) is a calculated value that helps assess the amount of free (bioactive) testosterone in the body, which is not bound to proteins like Sex Hormone-Binding Globulin (SHBG) or albumin, and is essential for functions like libido, muscle mass, and bone density.
. FTI is particularly useful in cases where SHBG levels are abnormal (e.g., in liver disease, obesity, or thyroid disorders), as these variations can significantly affect the interpretation of total testosterone levels that may not accurately reflect the bioactive hormone levels.
. It is used to evaluate conditions related to testosterone imbalance, such as hypogonadism, androgen excess (e.g., PCOS), and infertility.