As Testosterone Propionate is, of course, Testosterone, it suffers from moderate aromatization which results in the Estrogenic side effects of bloating, water retention, elevated blood pressure (as a result of the bloating), and risks of gynecomastia. This soft and puffy look that bloating brings to the physique is generally undesirable for most users that wish to engage in cutting cycles or lean mass cycles. Therefore, Testosterone Propionate must be utilized with an aromatase inhibitor in order to disable the aromatase enzyme and eliminate the water retention effect of the Estrogen conversion, which should result in a harder looking physique without the soft puffiness. In doing so, Testosterone can successfully be utilized as a ‘hardening’ and cutting compound, as well as for lean mass gains. Some individuals prefer the water retention, convinced that it aids in protecting tissues and connective tissue from the stressors of heavy strength gains and heavy lifting, and therefore Testosterone is preferred as a bulking and strength gaining compound in this case. In any case, Testosterone is also an excellent compound for all-out bulking and strength gaining cycles, which is what its main use seems to be among bodybuilders and athletes. It is a very versatile compound that can provide the anabolic strength necessary for bulking phases.
Because the ultimate goal of a steroid cycle is to increase strength and muscle size, the associated spike in estrogen which accompanies steroids such as Testosterone is considered undesirable. In order to disassociate the two effects, two classes of drug are used. Medications such as Nolvadex or Clomid target the estrogen receptors. They make it more difficult for the estrogen to exert it’s influence within the body thus allowing the testosterone to act more freely. The second class is aromatase inhibitors such as Femara. They target the aromatase enzyme itself in order to prevent the production of estrogen in the first place. Sometimes, it’s not always clear which option you should go with or even what the differences are between the two. Lets clear that up a little.
Testosterone esters were synthesized for the first time in 1936, and were found to have greatly improved potency relative to testosterone.  Among the esters synthesized, testosterone propionate was the most potent, and for this reason, was selected for further development, subsequently being marketed.  Testosterone propionate was introduced in 1937 by Schering AG in Germany under the brand name Testoviron.  It was the first ester of testosterone to be introduced,  and was the major form of testosterone used medically before 1960.  In the 1950s, longer-acting testosterone esters like testosterone enanthate and testosterone cypionate were introduced and superseded testosterone propionate.  Although rarely used nowadays due to its short duration,  testosterone propionate remains medically available.