Why is free testosterone measured instead of total testosterone?

Total testosterone includes SHBG-bound (inactive), albumin-bound (weakly active), and free (active) fractions. Free testosterone represents the biologically active portion. Conditions affecting SHBG (thyroid disease, obesity, liver disease) can dissociate total from free levels.

What is the Vermeulen equation?

The Vermeulen 1999 equation calculates free testosterone using total testosterone, SHBG, albumin (assuming 4.3 g/dL), and published binding constants. It is more accurate than the simpler FAI (Free Androgen Index) method.

What are normal free testosterone ranges?

Adult males: 50-210 pg/mL (174-729 pmol/L). Adult females: 1.0-8.5 pg/mL (3.5-29.5 pmol/L). Values vary significantly by age and laboratory method; always interpret with the assay-specific reference range.

Free Testosterone Calculation (Vermeulen)

Calculate free testosterone from total testosterone, SHBG, and albumin using Vermeulen 1999 equation. Normal free T males 50-210 pg/mL; females 1-8.5 pg/mL.

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Frequently Asked Questions

Why is free testosterone measured instead of total testosterone?

What is the Vermeulen equation?

What are normal free testosterone ranges?