Testosterone Propionate is a pure testosterone hormone. Although synthetic it is a perfect replica of the primary naturally produced male androgen testosterone. By design, the hormone is attached to the Propionate (propionic acid) ester, a small/short ester that enables the hormone’s release time to be controlled. Without an ester, the hormone would disperse and dissipate rapidly post administration. By attaching the ester, this promotes a controlled release and allows the individual to inject the hormone less frequently. Once Testosterone Propionate is injected, the ester slowly begins to detach from the hormone. As the ester is detached the testosterone hormone begins to release into the blood. The half-life of Testosterone Propionate is approximately two days, which is substantially longer than ester free testosterone, which carries a half-life a little less than 24 hours.