T Nation

Testosterone Types and Delivery

I stumbled across this article which answered many of my questions.

Hope somebody else get some use out of it…



1/2 life of the esters is related more to the solubility of the ester in water vs. oil than to the action of esterase.


So, generally, the more carbons the ester group has, the more soluble in oil it becomes, and the less soluble in water. The term for this ratio between oil and water solubility is called the “partition coefficient”-- the higher the solubility in oil, the higher the partition coefficient.

The partition coefficient of the ester in question is important because is effects how long the drug itself stays in the system…

Testosterone cypionate, on the other hand, has a high partition coefficient. When injected into the muscle, the drug remains in its esterified form in a deposit in the muscle tissue. From there, it will slowly enter the circulation as it is picked up in small quantities by the blood. Once the esterified testosterone is brought into the blood stream, “esterase enzymes” cleave off the ester chain in a process known as “hydrolization,” thus leaving the testosterone in its free form to perform its various actions and effects.