Supratherapeutical doses of anabolic androgenic steroids (AASs) have dramatic effects on metabolism in humans, and also inhibit feeding and reduce the rate of body weight gain in rats. In order to test the hypothesis that the AAS metabolic syndrome is accompanied by alterations in the central melanocortin system, we evaluated body weight, food intake and hypothalamic agouti-related protein (AgRP) and proopiomelanocortin (POMC) mRNA levels following administration of different doses of the anabolic androgenic steroid nandrolone decanoate. In order to distinguish changes induced by the steroid treatment per se from those resulting from the reduced food intake and growth rate, we also compared the effect of nandrolone decanoate on AgRP and POMC mRNA expression with both normally fed, and food restricted control groups. We here report that administration of nandrolone specifically reduces arcuate nucleus POMC mRNA levels while not affecting the expression level of AgRP. The effect on POMC expression was not observed in the food restricted controls, excluding the possibility that the observed effect was a mere response to the reduced food intake and body weight. These results raise the possibility that some of the metabolic and behavioural consequences of AAS abuse may be the result of alterations in the melanocortin system.