Testosterone injections are administered via esters. An ester is an organic compound where the hydrogen in the compound’s carboxyl group is replaced with a hydrocarbon group. Choosing the right ester is half the strategy in treating low-T, frequency & dosage then tailored to suit individual needs. Testosterone Enanthate and Testosterone Cypionate are 2 popular esters widely used for TRT therapy to treat primary and secondary hypogonadism or low-T.
Other esters are Undeconate, Propionate, Sustenol, and Nebido. Earlier Testosterone in the form of a powder was simply mixed in water to form a testosterone suspension and injected, which was extremely painful.
Is there a one size fits all TRT protocol?
There is no cookie cutter protocol that everyone is put on, but depending on physiological & lifestyle among other factors the optimum level that keeps one humming is arrived at by the doctor after a thorough blood work where several parameters are considered.
The holy grail of TRT therapy is to avoid peaks and valleys, or highs and lows and enable a steady testosterone boost to counter symptoms of low-T, so all systems keep chugging along nicely as painlessly as possible. No pain being the best option.
Staying close to how naturally testosterone in the body peaks early in the morning, and a small bit late at noon is the best testosterone therapy.
Disruption of these patterns disrupts cell differentiation of Leydig cells, size of testes during puberty, among other negative effects as per a recent study in animal models.
Testosterone enanthate & Testosterone cypionate are very similar and preferred low-T treatment (via injections) options.
Enanthate works wonders in achieving stable levels while keeping potential side effects manageable. With a short half life most side effects can be managed by altering dosage or frequency or both.
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Chemical structure of Testosterone Cypionate & Testosterone Enanthate
In terms of chemical structure, they are very similar except testosterone cypionate has an additional carbon atom which makes its half life a bit longer, 8 days while Testosterone Enanthate about 7 days.
Carrier oil used in Testosterone Cypionate and Testosterone Enanthate
The carrier oil used is another major difference. Sesame oil makes Testosterone Enanthate highly viscous, and can be painful for subcutaneous injections. Long term patient compliance with this protocol is also an issue since preparing the injection is time consuming. Painful lumps due to the high viscosity can be a problem for a few from testosterone enanthate. The 5% Chlorobutanol used as a preservative in T enanthate causes high skin irritation. This is a very high percentage than the normally allowed .5%% which is not tolerated by a few.
Olive oil or cottonseed oil used in Testosterone Cypionate makes it easier to inject subcutaneously since they are more fluid. Injections via the subcutaneous route are less painful than intramuscular injections. Absorption is slower which makes it stable, decreases aromatisation of testosterone and DHT conversion so that side effects of excess oestrogen production - gynecomastia, fluid retention need not be dealt with.
Intramuscular or Subcutaneous?
In short, the significant difference between Testosterone Cypionate & Testosterone Enanthate is one of injecting intramuscularly or subcutaneously. High viscosity of T-enanthate makes it harder to inject subcutaneously which is a superior way to achieve stable levels of serum testosterone avoiding peaks & troughs and minimize side effects. While injecting intramuscular absorption is quicker due to increased vascular exposure which hastens the testosterone into the system faster, which also means peaks & valleys, and unwanted estrogen and DHT as a result of 5 alpha reductase enzyme breaking down testosterone which may result in hair loss, acne, prostate irritation or enlargement.
In the end...
Considering all the above factors Testosterone Cypionate injected subcutaneously seems to be a better option due to the carrier oil being more fluid, but individual preference, life style & physiological factors like bulk of a person will dictate whether intramuscular is a better option, in which case Enanthate is the choice of Testosterone injection. What suits one best is the ideal ester and ultimately nothing is set in stone.