The use of AAS have been associated numerous changes in physiological function (Yesalis et al 1989; Kleiner 1991). Anabolic steroids can increase strength and muscle mass when accompanied by adequate protein, calories and intense training (Freed, Banks, Longson, & Burley, 1975; Kleiner, 1991; Landry & Primos, 1990; American College of Sport Medicine, 1987). Anabolic steroids improve nitrogen utilization and promote positive nitrogen balance by the reversal of catabolic processes. Anabolic steroids can improve nitrogen balance and increase the concentration of total plasma amino acids. This seems to be due to an amino acid saving mechanism with a renal site of action (Kleiner, 1991; Hausmann, Nutz, Rommelsheim, Caspari, & Mosebach, 1990). Intense training can serve to maintain a relative state of chronic catabolism. Therefore, the requirements for protein and calories appear to increase when training with the aid of anabolic steroids (Freed, Banks, Longson, & Burley, 1975; Kleiner, 1991). A protein intake of 12% to 20% of the total calories has been recommended for athletes (Paul, 1989). The protein and calorie requirements for bodybuilders using steroids are unknown (Kleiner, 1991; Kleiner, Bazzarre, & Litchford, 1990).

Anabolic steroids may play a physiological role in the regulation of fatty acid oxidation in liver and fast twitch muscle mitochondria even in the absence of intense physical training (Guzman, Saborido, Castro, Molano, & Megias, 1991).

Anabolic-androgenic steroid use may alter glucose tolerance, and induce hyperinsulinism (Yesalis, Wright, & Bahrke, 1989). Powerlifters using anabolic steroids have been shown to develop insulin resistance and diminished glucose tolerance (Cohen, & Hickman, 1987). Although chronic exercise generally decreases serum insulin levels (Viru, Karelson, & Smirnova, 1992), this is accompanied by an increase peripheral insulin sensitivity (Richter, Mikines, Galbo, & Keins, 1989).

Men have been shown to be more susceptible to gynecomastia as a result of anabolic-androgenic steroid use (Yesalis, Wright, & Bahrke, 1989). Gynecomastia in athletes has been associated with the increase of serum estradiol concentrations during the use of anabolic-androgenic steroids (Alen, Reinila, Vihko, & Reijo, 1985).

Alen, Reinila, & Reijo (1985) observed that serum testosterone level tended to increase throughout a 26 week cycle of various AAS until abruptly dropping below normal levels during cessation. When athletes discontinue the use of AAS they experience a refractory period where they do not produce physiological amounts of endogenous testosterone (Di Pasquale, 1992a). Anabolic-androgenic steroid can reduce endogenous testosterone, gonadotrophic hormones and sex hormone-binding globulin (Yesalis, Wright, & Bahrke, 1989). Weight trained athletes have been shown to have low serum testosterone concentrations immediately after cessation of a AAS cycle but return to normal within weeks (Alen, Reinila, & Reijo, 1985).

Hurley, Seals, Hagberg, Goldberg, Ostrove, Holloszy, Wiest, & Goldberg (1984) found that oral AAS significantly decreased both free and total serum testosterone levels. In contrast, injectable AAS significantly increased free and total serum testosterone level when taken alone or in combination with an the oral form. Interestingly, serum testosterone levels have been linked to aggressive behavior in animals and humans (Bahrke, Barke, & Strauss, 1990).