Primary polydipsia Alcoholism may cause physiological thirst since ethanol inhibits vasopressin, the hormone primarily responsible for water retention in osmoregulation. The following conditions should also be excluded: DI, cerebral salt wasting, pseudohyponatraemia caused by hyperlipidemia or hyperparaproteinemia, SIADH, mineralcorticoid deficiency, salt-wasting nephropathy, nephrotic syndrome, chronic heart failure and cirrhosis. Tobacco smoking is an often overlooked factor linked to hyponatremia, due to the ADH-releasing effect of nicotine, although this is usually limited to heavy smokers. One study suggested that around 70% of patients with self-induced polydipsia were tobacco smokers. Diagnostic tests for primary polydipsia usually involves the fluid deprivation test to exclude ADH
Functional symptom Functional symptom A functional symptom is a medical symptom, with no known physical cause. It arises from a problem in the ‘functioning’ of the nervous system, and not due to a structural or pathologically defined disease. Functional symptoms are increasingly viewed within a framework in which psychological, physiological and biological factors should be considered to be relevant. Historically, there has often been fierce debate about whether certain problems are predominantly related to an abnormality of structure (disease) or function (abnormal nervous system functioning), and what are at one stage posited to be functional symptoms are sometimes later reclassified as organic,