Testosterone Propionate is simply Testosterone with the Propionate ester bound to the Testosterone chemical structure. Specifically Propionate is Propionic acid, but once bound to Testosterone it is properly referred to in chemistry as an ester bond (or ester linkage). Propanoic acid is bonded to the 17-beta hydroxyl group on the Testosterone structure. Esterified anabolic steroids are more fat soluble, and release slowly from the injection site – however, this is not the main reason as to why esters extend the release rate of the anabolic steroid. The primary reason for the augmentation of its half-life and release rate is because once Testosterone Propionate enters the bloodstream, enzymes work to break the bond between the ester and the hormone, which takes a varying amount of time. The end result is that the ester is removed from the hormone by enzymes, and what is left is pure Testosterone that is free to do its work in the body. This process of enzymes cleaving off the ester from the Testosterone molecule is what is responsible for the slower release rates. Testosterone alone with no ester bonded to it possesses a half-life of approximately 2 – 4 hours. When the Propionate ester is attached to it, creating Testosterone Propionate, the half-life of Testosterone is now extended to 4.5 days, providing a slower release and activity of the hormone.

Properties of Testosterone Propionate
The properties of Testosterone Propionate are what any individual would expect from any other type of Testosterone preparation, with the exception of the differing release rates and half-life. Testosterone is what could be considered quite literally the original anabolic steroid, which is manufactured endogenously naturally in all humans and in the vast majority of animal species.
Because of this, Testosterone is considered the safest anabolic steroid for use, as every individuals body is already accustomed to the effects of Testosterone only to a lesser degree.
Essentially, the use of Testosterone for the purpose of physique and performance enhancement is simply the supplementation of additional hormones – the act of inserting more of a hormone into the body that it already manufactures and uses