Description

Free testosterone refers to the fraction of testosterone in the bloodstream that is not bound to proteins, such as albumin or sex hormone-binding globulin (SHBG). It represents the biologically active form of testosterone that is available to exert its effects on tissues and cells throughout the body.

Measuring free testosterone levels is important for assessing androgen status, particularly in conditions where total testosterone levels may be misleading due to variations in protein binding. For example:

1. Hypogonadism: Low levels of total testosterone may not accurately reflect androgen deficiency if SHBG levels are elevated, leading to normal or elevated total testosterone levels but reduced levels of free testosterone. Measuring free testosterone helps in diagnosing hypogonadism in such cases.
2. Polycystic Ovary Syndrome (PCOS): Women with PCOS may have elevated levels of total testosterone due to increased ovarian androgen production, but their free testosterone levels may be within the normal range. Measuring free testosterone can help differentiate between true hyperandrogenism and normal physiological variations.
3. Monitoring Testosterone Replacement Therapy (TRT): In men receiving TRT, monitoring free testosterone levels can help ensure that adequate levels of bioavailable testosterone are achieved while minimizing the risk of side effects associated with supraphysiological testosterone levels.

Free testosterone levels can be measured using various laboratory methods, such as equilibrium dialysis, ultrafiltration, or calculated algorithms based on total testosterone, SHBG, and albumin levels. However, it’s essential to use validated and reliable assays for accurate measurement of free testosterone levels.

Interpretation of free testosterone levels should be done in conjunction with clinical symptoms and other hormone levels, as individual variability and assay methods can influence results. Consulting with a healthcare provider experienced in hormone assessment is recommended for proper interpretation and management based on free testosterone levels.