This analysis of the symptomatology of Anorexia Nervosa (AN) in neuroanatomical, neurophysiological, behavioral pharmacology and systemstheory terms, provides strong arguments for a fundamental Homeostasis disorder. The role of the monaminergic structures in the regulation of Homeostasis is discussed. After an interpretation of the AN-symptomatology in monaminergic terms the author concludes to a noradrenergic deficit and a dopaminergic overshoot in AN; this points to Dopamine-betahydroxylase, the dopamine-noradrenalin converting enzyme; a dificiency of the cofactor copper is proposed. Treatment by coppersulphate for noradrenergic stimulation and/or pimozide for dopaminergic receptor blockade has been tested in three cases of AN; the clinical and biological results are in accordance with the predictions. The author concludes to a special setpointregulation by noradrenalin of Homeostasis in AN, consolidated by dopaminergic mediated reinforcement of this contingent behavior.