Chronic fatigue disorders: an inappropriate response to arginine vasopressin?

Chronic fatigue disorders are characterized by a subjectively defined group of symptoms such as chronic fatigue, mental confusion, exertional malaise, weight changes, and/or diffuse multi-joint pains. Significant clinical overlap exists between chronic fatigue disorders and the syndrome of serum inappropriate anti-diuretic hormone (SIADH). Both chronic fatigue disorders and SIADH are characterized by lethargy and mental confusion. Both disorders can be induced or exacerbated by viral illnesses, physical exertion, emotional stress and/or hypotension. Both can be treated with salt loading and glucocorticoids. Therefore, altered water metabolism resulting from inappropriate release and/or response to arginine vasopressin (AVP) is proposed as a pathophysiological basis of certain chronic fatigue disorders. Moreover, these data suggest that salt loading and/or direct inhibition of AVP may be an effective therapeutic approach in individuals with chronic fatigue disorders.