Among transgender men, patients who had previously used IM testosterone therapy with long-acting esters did not want to revert back to IM injections after they were started on SC testosterone therapy (24, 28, 51). Indeed, long-term compliance among men who are prescribed testosterone therapy with IM injections is low; approximately 69% of men on long-acting esters discontinue treatment within 3 months of therapy, and 95% discontinue it within 12 months (56). In this review, we summarize the published data on the pharmacokinetics and safety of SC administration of both long-acting (enanthate and cypionate) and ultralong-acting (undecanoate) testosterone esters in hypogonadal and transgender men. In the mid-1950s, the longer-acting testosterone esters testosterone enanthate and testosterone cypionate were introduced. Studies that have assessed patient preference regarding the route of administration of testosterone esters (enanthate and cypionate) suggest that patients generally prefer the SC route compared to the IM route (24, 28, 51). Because of the longer absorption time, it was introduced as an option to minimize peaks and troughs in serum testosterone levels after dosing, as well as to reduce the frequency of injections in men with organic androgen deficiency who require long-term testosterone therapy. Ester weight reduces the proportion of active testosterone in each mg. This results in a wide range of half-lives, injection frequencies, and onset profiles that bodybuilders and clinicians leverage according to goals, side effect profiles, and lifestyle compatibility. LS-1727 is a nitrosocarbamate ester of nandrolone that was developed as a cytostatic antineoplastic agent but was never marketed. Sturamustine is a nitrosourea ester of dehydroepiandrosterone (DHEA) that was developed as a cytostatic antineoplastic agent but was never marketed. The term ester is often used in the language of testosterone replacement therapy. You've come to our clinic after hearing about the benefits of testosterone replacement therapy (TRT), and you'd like to learn more before trying the treatment. Similar to IM injections, periodic monitoring of the patients for risks and benefits should continue as recommended by clinical practice guidelines (1). Patients should be informed that currently, data and experience with SC testosterone therapy both are limited. Once a patient qualifies for testosterone therapy (1, 2), risks and benefits of therapy as well as pros and cons of each formulation should be discussed (see Table 1). Short esters break down quickly, requiring frequent administration, while long esters take longer to release, reducing injection frequency. Understanding the various aspects of testosterone and its treatments is crucial for those experiencing low levels of this vital hormone. Testosterone Enanthate is another long-acting ester commonly used in testosterone replacement therapy. This improvement is significant because it slows the release of testosterone once it is injected into the body. Esters improve the solubility of testosterone in oil. These components are all testosterone and contain identical molecules. Long-acting testosterone undecanoate suits men who prefer fewer injections and stable levels. For example, with short-acting esters like cypionate or enanthate, blood should typically be drawn the morning before the next injection. Understanding these kinetic profiles is essential, because the pattern of peaks and troughs directly affects how patients feel between doses.Testosterone enanthate and cypionate are the most widely used short – to medium-acting esters. It was not until 1991 that studies dissolving testosterone undecanoate in tea seed oil revealed the medication had a prolonged duration of action compared to other testosterone esters. This explains how testosterone enanthate, testosterone propionate, testosterone cypionate and testosterone undecanoate all have different half-lives. The undesired effects of IM testosterone injections are the large fluctuations in testosterone levels, injection site discomfort, and elevated risk for erythrocytosis. Two recently approved formulations—a subcutaneous auto-injection of testosterone enanthate (19), and oral testosterone undecanoate capsules (20)—come with a black box warning for blood pressure increases.
