The procedure for calculating free testosterone
To calculate the free testosterone is used:
- The albumin concentration level indicator (in the absence of laboratory data, a constant albumin concentration is used - 4.3 g / dl).
- Total testosterone level.
- An indicator of the level of globulin that binds sex steroids (SHGP, SSSG - SHBG).
Enter the available albumin, testosterone and SHBG levels in the appropriate fields by selecting the appropriate units of measure. After filling in all the fields, click on the “Calculate” button, then in the “Results” field you will receive the values of free and biologically available testosterone.
A warning! The data for calculated free and bioavailable testosterone are reliable in most clinical situations, but the calculator should not be used for physiological and pharmacological increases in androgens (for example, in girls during menstruation, and in men during testosterone treatment).
The calculator is developed at the Department of Hormonology, University Hospital of Ghent, Belgium.
Testosterone Forms (Fractions)
There are three forms of testosterone:
- ; Associated with GPSS - inactive form (about 57%) ;
- ; Albumin-associated - active (bioavailable) form (about 40%) ;
- . Free testosterone - has maximum bioavailability (1-3%) .
Thus, the level of total testosterone indicates a quantitative indicator of all forms of T in the blood, and in some cases can not be used as a defining indicator of the degree of androgen deficiency, because the level of total testosterone can remain normal, while T of an inactive form will prevail over its bioavailable fraction.
It is bioavailable forms of T have an effect on the body, because able to penetrate androgen-sensitive cells, which can not T associated with GPSS, due to their strong connection.
Methods for determining the level of free testosterone
Table 1 - Methods for determining the level of free testosterone (Dedov II, Kalinchenko S.Yu., 2006)
|Dual (Equilibrium) Dialysis||+||+++||+|
|Radioimmunological analysis (RIA)||++||+||++|
|Determination of calculated free testosterone||+++||+++||+++|
|Determination of the concentration of free testosterone in saliva||++||+++||++|
Since modern methods for determining free testosterone are time consuming and inaccessible (Table 1), the determination of calculated free testosterone is the method of choice because of its availability and reliability.