Free Testosterone(FT)

Symptoms of androgen deficiency, low libido, erectile dysfunction, fatigue, reduced muscle mass, depressed mood, correlate more reliably with free testosterone than with total testosterone in most published cohorts. A man with a total testosterone of 600 ng/dL and a high SHBG of 80 nmol/L may have a calculated free T below 8 ng/dL and be symptomatic, while another man with a total of 450 ng/dL and a low SHBG of 20 nmol/L can have a free T of 12 ng/dL and feel asymptomatic. The Vermeulen calculation (free T derived from total T, SHBG, and albumin) is considered the practical gold standard for most clinical purposes; it correlates closely with equilibrium dialysis, the research reference method, at a fraction of the cost. Direct free T immunoassays are widely available but vary substantially between labs and are not recommended by the Endocrine Society for clinical decision-making. Typical reference ranges run from roughly 9 to 30 ng/dL in healthy adult men, with a steady age-related decline of roughly 1 to 2 percent per year after age 30. Optimal targets on TRT vary by clinician but generally aim for the upper half of the age-matched reference range rather than supraphysiologic levels.