AAS are a class of hormones synthesized from cholesterol that share a similar chemical structure.  They are any of numerous naturally occurring or synthetic compounds having as basis 17 carbon atoms arranged in four rings. All AAS derivates are four-ringed structures with 19 carbon atoms. The isolation of testosterone and confirmation of its role in normal human development led clinicians to explore the benefits of its use for the treatment of various human disorders. Testosterone itself exhibits a very low bioavailability after oral administration.

Early attempts to utilize clinically orally administered testosterone were unsuccessful because it rapidly degraded during its first pass through the liver, resulting in subtherapeutic amounts of the molecule reaching target tissues. To overcome this problem, the testosterone molecule was modified to produce synthetic androgens that had slower hepatic metabolism and longer systemic exposure. Modification of testosterone was also aimed to enhance testosterone's anabolic effects while reducing its androgenic properties.

The result of these efforts was the development of testosterone analogues. Anabolic androgenic steroids (AAS) have both anabolic and androgenic properties and are synthetic derivates of the endogenous primarily male steroid hormone, testosterone and exert their effects via activation of the same androgen receptor. This includes testosterone, testosterone cypionate, testosterone enanthate, testosterone undecanoate, nandrolone decanoate, oxandrolone, and oxymetholone.

The clinically significant classes of testosterone analogues are the (1) 17 beta-esters (e.g., testosterone propionate), (2) 17 alpha-alkylated anabolic-androgenic steroids (e.g., oxandrolone or oxymetholone), and (3) 19-nortestosterone anabolic-androgen steroids (e.g., nandrolone decanoate). The principal anabolic-androgenic steroids in use in the United States are testosterone cypionate, testosterone enanthate, nandrolone decanoate, oxandrolone, and oxymetholone.

Hershberger Assay

Most of the earlier assays of bioactivity of androgenic compounds were based on in vivo responses, e.g. the growth of capon comb or accessory sex organs of male rats. The so-called Hershberger assay [Hershberger LG, Shipley EG, Meyer RK. Myotrophic activity of 19-nortestosterone and other steroids determined by modified levator ani muscle method. Proc Soc Exp Biol Med 1953;83(1):175-80. ], widely used in drug and chemical testing, measures androgenic and antiandrogenic activity in castrated mice or rats by monitoring the weight response of their androgen dependent tissues, such as the levator ani muscle, prostate or seminal vesicles. The higher the androgenic dose of a sample the higher is the weight gain of the organs. These assays are very specific but slow, labor-intensive, expensive and in breach with the current trend of reducing the usage of live animals. When Hershberger assay is used to measure antiandrogenic activity, prepubertal rats are treated with androgen, and the antiandrogenic activity is reflected by the degree of inhibition of the androgen effect.



Selective Androgen Receptor Modulators (SARMs) are a novel class of AR ligands that possess tissue-selective pharmacological activities. SARMs of various chemical structures have been discovered and characterized, and lead compounds with much improved specificity for AR, in vivo pharmacokinetic profiles, and higher degree of tissue selectivity have entered clinical development, and are expected to dramatically expand the clinical applications of androgens.

The major purpose in developing non-steroidal SARMs is to achieve tissue-selective modulation of AR action, thus, mini­mizing undesirable side effects that are normally associated with steroidal androgens and capitalizing on more potent anabolic effects to exploit previously untenable therapeutic applications of AR ligands. An ideal SARM should also have the following features: i) high specificity for the AR; ii) improved oral bioavailability and a pharmacokinetic profile that allows once-a-day admin­istration and, most importantly; and iii) desirable, tissue-selective pharmacological activities.



Among the various pathways sought by drug traffic, the Internet is probably the main worldwide channel for easy access to drugs and other substances. A survey in 1955 US-based male non-medical AAS users showed that more than half of the sample had purchased AAS over the Internet, and in another survey, posted on the message boards of Internet websites popular among AAS users, >70% of the respondents indicated Internet as their drug source. Circumstantial evidence indeed suggests that Internet is possibly the primary means for buying and selling illicit AAS and a primary source of non-medical AAS information.



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