What are free and bioavailable testosterone?
Testosterone is present in the blood as “free” testosterone (1-4%) or bound testosterone. The latter may be loosely bound to albumin, a serum protein, or bound to a specific binding protein called Sex Steroid Binding Globulin (SSBG) or Sex Hormone Binding Globulin (SHBG). The binding between testosterone and albumin is not very strong and is easily reversed; so the term bioavailable testosterone (BAT) refers to the sum of free testosterone plus albumin-bound testosterone. Alternatively, it is the fraction of circulating testosterone that is not bound to SHBG. It is suggested that BAT represents the fraction of circulating testosterone that readily enters cells and better reflects the bioactivity of testosterone than does the simple measurement of serum total testosterone. Also, varying levels of SHBG can result in inaccurate measurements of BAT. Decreased SHBG levels can be seen in obesity, hypothyroidism, androgen use, and nephritic syndrome. Increased levels are seen in cirrhosis, hy
Related Questions
- The bioavailable testosterone is normal even though the free testosterone is low. How do we determine what the best replacement amount and the best dosing schedule?
- What is the difference between free testosterone and bioavailable testosterone?
- Does having high levels of free testosterone raise the risk if Prostate Cancer?
