Circulating Testosterone consists of testosterone bound to SHBG and the bioavailable (Free & Bound to Albumin). The latter is biologically active. In men approximately 40% of Total testosterone is albumin bound while in women approximately 20% is albumin bound. Free testosterone can be used as second-level test for suspected increases or decreases in physiologically active testosterone. This test helps to assess androgen status in cases with suspected or known Sex hormone-binding globulin-binding abnormalities; assesses functional circulating testosterone in early pubertal boys and older men; assesses functional circulating testosterone in women with symptoms or signs of hyperandrogenism but normal total testosterone levels.