Patients with Addison's disease have an increased basal level of plasma arginine vasopressin (AVP), together with a decreased osmotic threshold. This disturbance of osmoregulation of AVP is likely to play a major role in the failure to excrete a water load, which is a characteristic feature of Addison's disease.
It is worth screening patients with idiopathic Addison's disease for other associated diseases since approximately fifty per cent of them will have, or will develop, either autoimmune thyroid disease or insulin-dependent diabetes mellitus.
