ABSTRACT
According to the World Anti-Doping Agency (WADA) Prohibited List, the S1 and S2 classes of doping agents are composed of, by and large, naturally occurring hormones and their synthetic derivatives (WADA 2014 ). The S4 class of hormone and metabolic modulators ( Table 8.1 ) contains several groups of synthetic compounds, which act by modulating various endogenous hormonal pathways and local muscle-speci¿ c transduction pathways. In most cases, the aim of such modulators is to enhance exercise performance; however, in the case of aromatase inhibitors, selective oestrogen receptor modulators (SERMs), or other antioestrogenic substances, the aim may be to counteract the unwanted side effects of anabolic androgenic steroid (AAS) administration.
