Sex hormones
Free testosterone (calculated)
Bioavailable testosterone; preferred when SHBG is altered.
Sample
Serum
Clinical reference range
50 to 210 pg/mL
Adult male
Conv: 50–210 pg/mL
Biology
What it measures
~2% of total testosterone is free; ~44% bound to SHBG, ~54% albumin-bound. Free + albumin = bioavailable.
Clinical use
Why we order it
Male hypogonadism workup when SHBG is altered (obesity, hyperthyroidism, hepatic disease, T2DM).
Pitfalls
Pre-analytic & interpretation traps
- !Direct analog free-T immunoassays are unreliable — use equilibrium dialysis or calculated free-T (Vermeulen).
Related