Thread: What is "Free Testosterone"?

Ask Bill Roberts: What is "Free Testosterone"?

Question:
What is free testosterone and does Proviron increase free test levels?


Answer: Well, let’s leave out the Proviron part as Proviron does not increase free testosterone.

The “free concentration” of a drug is that amount which is dissolved in a given volume of the aqueous (water) part of the blood.

Not complexed with other molecules, or dissolved in fat, or any such thing, but dissolved as free molecules in solution.

The free concentration fully predicts the activity of the drug, and in fact the free concentration, combined with amounts of other things such as binding proteins, is what determines the total.

Not the total determining the free.

Other concentrations, such as total, are not valid predictors of activity.

This, in practice, proves to be an almost impossible point to get across.

But by illustration, suppose that there was a test that measured “really total” testosterone. In other words, absolutely all of the testosterone in the body.

Well, in that case a fat man would almost always have far more “really total” testosterone than a lean man.

But does it make the tiniest difference to the androgen receptors that he has more testosterone dissolved in fat? No, absolutely none.

The only thing that matters to them is the free concentration.

Any binding equation you will find will not even have a term for total concentration, or amount bound to binding proteins etc: only free concentration. Because it gives the complete information regarding the chemical activity.

And one shouldn’t be deceived by the term “bioavailable testosterone”: this term is a product of ignorance. (No matter that there are MD’s that use it.)

It is the free value that in fact tells the story of the concentration that the receptors “see.”

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Another great post from this guy!