Polydipsia is excessive thirst or excess drinking. The word derives from the Greek πολυδίψιος (poludípsios) "very thirsty", which is derived from πολύς (polús, "much, many") + δίψα (dípsa, "thirst"). Polydipsia is a nonspecific symptom in various medical disorders. It also occurs as an abnormal behaviour in some non-human animals, such as in birds. Causes
Diabetes
Polydipsia can be characteristic of diabetes mellitus, often as an initial symptom. It is observed in cases of poorly controlled diabetes, which is sometimes the result of low patient adherence to anti-diabetic medication.Diabetes insipidus ("tasteless" diabetes, as opposed to diabetes mellitus) can also cause polydipsia. Other physiological causes
It can also be caused by a change in the osmolality of the extracellular fluids of the body, hypokalemia, decreased blood volume (as occurs during major hemorrhage), and other conditions that create a water deficit. This is usually a result of osmotic diuresis. Polydipsia is also a symptom of anticholinergic poisoning. Zinc is also known to reduce symptoms of polydipsia by causing the body to absorb fluids more efficiently (reduction of diarrhea, induces constipation) and it causes the body to retain more sodium; thus a zinc deficiency can be a possible cause. The combination of polydipsia and (nocturnal) polyuria is also seen in (primary) hyperaldosteronism (which often goes with hypokalemia). Antipsychotics can have side effects such as dry mouth that may make the patient feel thirsty. Primary polydipsia
Primary polydipsia describes excessive thirst and water intake caused in the absence of physiological stimuli to drink.
However, prior to a water deprivation test, consideration should be given to a psychiatric consult to see whether it is possible to rule out psychogenic polydipsia or habit polydipsia. Diagnosis
Polydipsia is a symptom (evidence of a disease state), not a disease in itself. As it is often accompanied by polyuria (excessive urination) and low sodium levels. Investigations directed at diagnosing diabetes insipidus and diabetes mellitus can be useful. Blood serum tests can also provide useful information about the osmolality of the bodys extracellular fluids. A decrease in osmolality caused by excess water intake will decrease the serum concentration of red blood cells, blood urea nitrogen (BUN), and sodium. See also
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