Side effects of testosterone enanthate include virilization among others.[5] Approximately 10 percent of testosterone enanthate will be converted to 5α-dihydrotestosterone in normal men.[17] 5α-Dihydrotestosterone (DHT) can promote masculine characteristics in both males and females. These masculine characteristics include: clitoral hypertrophy, androgenic alopecia, growth of body hair and deepening of the vocal cords. Dihydrotestosterone also plays an important role in male sexual function and may also be a contributing factor of ischemic priapism in males as shown in a study conducted on the use of finasteride to treat ischemic priapism in males. Testosterone enanthate can also lead to an increase in IGF-1 and IGFBP.[18][19] Testosterone enanthate can also be converted to estradiol (E2) by the aromatase enzyme,[20] which may lead to gynecomastia in males. Aromatase inhibitors, such as anastrozole, letrozole, exemestane, etc., can help to prevent the subsequent estrogenic activity of testosterone enanthate metabolites in the body.[20]
Testosterone enanthate is converted by the body to testosterone that has both androgenic effects and anabolic effects;[5] still, the relative potency of these effects can depend on various factors and is a topic of ongoing research.[21][22]Esterase enzymes break the ester bond in testosterone enantate, releasing free testosterone and enanthic acid through hydrolysis. This process ensures a sustained release of free bioavailable and bioactive testosterone in the body. Testosterone can either directly exert effects on target tissues or be metabolized by the 5α-reductase enzymes into 5α-dihydrotestosterone (DHT) or aromatized to estradiol (E2).[21] Aromatization in this context is the process where testosterone is converted to estradiol (E2) by the enzyme aromatase (CYP19A1 in humans). This conversion involves changing the structure of testosterone to include an aromatic ring A of a steroid nucleus, making it an estrogen, a so-called female hormone, which plays various roles in the body, such as regulating reproductive functions and bone density. If not aromatized (not converted into an estrogen), both testosterone and DHT are bioactive and bind to an androgen receptor; however, DHT has a stronger binding affinity than testosterone and may have more androgenic effect in certain tissues (such as prostate gland, skin and hair follicles)[23] at lower levels.[21]
Testosterone enanthate has an elimination half-life of 4.5 days and a mean residence time of 8.5 days when used as a depot intramuscular injection.[2] It requires frequent administration of approximately once per week, and large fluctuations in testosterone levels result with it, with levels initially being elevated and supraphysiological.[2] When testosterone enanthate is dissolved in an oil (such as castor oil), the oil acts as a depot, or reservoir, that slowly releases the drug into the bloodstream. This slow release is due to the oil's viscosity and the gradual breakdown of the ester bond by esterase enzymes. The oil creates a barrier that slows the diffusion of testosterone enanthate into the surrounding tissues, resulting in a more controlled and prolonged release compared to injecting pure testosterone enanthate.[24][25] The rate at which testosterone enanthate is released from oils can vary based on the oil's viscosity and other properties such as drug solubility in the oil.[26][27][28][29]
Testosterone enanthate was described as early as 1952[32] and was first introduced for medical use in the United States in 1954 under the brand name Delatestryl.[14][4]
Testosterone enanthate is the generic name of the drug and its USANTooltip United States Adopted Name and BANTooltip British Approved Name.[30][31][33][34] It has also referred to as testosterone heptanoate.[30][31][33][34]
Testosterone enanthate is available in the United States and widely elsewhere throughout the world.[36][31][34] Testosterone enanthate (testosterone heptanoate) is often available in concentrations of 200 mg per milliliter of fluid.[37]
On October 1, 2018, the U.S. Food and Drug Administration (FDA) announced the approval of Xyosted. Xyosted, a product of Antares Pharma, Inc., is a single-use disposable auto-injector that dispenses testosterone enanthate. Xyosted is the first FDA-approved subcutaneous testosterone enanthate product for testosterone replacement therapy in adult males.[41]
^ abcdLuetjens CM, Wistuba J, Weinbauer G, Nieschlag E (2007). "The Leydig Cell as a Target for Male Contraception". The Leydig Cell in Health and Disease. Contemporary Endocrinology. Humana Press. pp. 415–442. doi:10.1007/978-1-59745-453-7_29. ISBN978-1-58829-754-9.
^Ashton WS, Degnan BM, Daniel A, Francis GL (1995). "Testosterone increases insulin-like growth factor-1 and insulin-like growth factor-binding protein". Annals of Clinical and Laboratory Science. 25 (5): 381–388. PMID7486812.
^Hoeh MP, Levine LA (March 2015). "Management of Recurrent Ischemic Priapism 2014: A Complex Condition with Devastating Consequences". Sexual Medicine Reviews. 3 (1): 24–35. doi:10.1002/smrj.37. PMID27784569. S2CID24028084.
^ abIshikawa T, Glidewell-Kenney C, Jameson JL (February 2006). "Aromatase-independent testosterone conversion into estrogenic steroids is inhibited by a 5 alpha-reductase inhibitor". The Journal of Steroid Biochemistry and Molecular Biology. 98 (2–3): 133–138. doi:10.1016/j.jsbmb.2005.09.004. PMID16386416. S2CID25849126.
^ abcdMorton IK, Hall JM (6 December 2012). "Testosterone". Concise Dictionary of Pharmacological Agents: Properties and Synonyms. Springer Science & Business Media. p. 270. ISBN978-94-011-4439-1. Archived from the original on 4 October 2024. Retrieved 11 May 2019.
^ abcde"Testosterone". Drugs.com. October 1, 2018. Archived from the original on November 13, 2016. Retrieved December 5, 2018.