In everyday life, we physiologically lose a large amount of fluid through the skin, lungs and kidney; the range of this loss varies depending on environmental and body temperature, physical activity, antidiuretic response (fluid retention), or food intake.

The body works to ensure that the volume of fluid intake is sufficient to replace the usual loss in order to maintain the balance of the body.  

One of the physiological responses of the body aims to activate endocrine systems that allow controlling the level of absorption or renal excretion of water and electrolytes, facilitating the conservation or elimination of fluids, and the conduct of seeking and consuming fluids itself, but in other cases Sometimes thirst or more specifically excessive thirst has a pathological origin, because the corrective mechanisms can be altered, generating a variety of clinical pictures.

The excessive thirst or polidpsia is the persistent feeling of thirst, which forces people to drink water or any other liquid almost constantly and disproportionately. This is accompanied by large fluid losses in the form of urine (polyuria).

In this case, excessive thirst is considered secondary to polyuria, that is, it is the result of deterioration in the mechanism of fluid conservation in the body.

Causes of excessive thirst

Common causes could be: very salty food, dehydration due to diarrhea, dehydration due to fever, dry mouth or xerostomia could also cause excessive thirst. But there are other conditions that can cause polydipsia.

Mellitus diabetes

The most common manifestation of this disease is the excessive loss of fluid through the urine, which usually causes  excessive and permanent thirst in the person who suffers from it. Diabetes increases the levels of glucose (sugar) in the blood, which causes the kidney to eliminate more fluid and thus excess glucose.

Diabetes insipidus

In diabetes insipidus, there is a significant reduction in the synthesis, storage and release of vasopressin (ADH) or also due to the renal inability to respond to the action of available antidiuretic hormone (ADH), resulting in uncontrolled or lost polyuria in both cases. disproportionate fluid, and secondarily excessive thirst .

Primary polydipsia

It is a regulatory alteration, which arises from the inappropriate activation of the mechanisms of thirst, without being the main cause the pathological losses of liquid. These are now people who suffer from excessive thirst, despite having normal or supernormal hydration levels.  

Primary polydipsia can be generated by an accident or head trauma, or after the consumption of chemicals such as lithium or alcohol, in this case we would be facing a dipsogenic polydipsia, the person manifests excessive thirst at all times , leading to a reduction considerable plasma concentration (hyponatremia), which prevents the release of ADH, and as a result a significant loss of fluids. This scenario causes the patient to remain in a state of chronic thirst, polydipsia and polyuria.

On the other hand, psychogenic polydipsia is quite common among the psychiatric population and, especially, among people suffering from schizophrenia. Compulsive water consumption usually occurs simultaneously with an explicit denial of thirst by patients and, despite this, very high volumes of water intake.

Some research has suggested that the cause of raw polydipsia could be the syndrome of inappropriate ADH secretion (SIADH) characterized by inappropriately high levels of ADH in situations where it should be suppressed by low plasma osmolality. This syndrome is common to observe in patients with psychiatric illnesses and head injuries.

Gestational polydipsia

It generally occurs during the first trimester of pregnancy, at which time certain hormonal factors associated with pregnancy could be activated and be responsible for alterations in fluid intake. These people have been shown to show an absence of renal response to vasopressin. 

Some research attributes the cause to the possible action of vasopressinase, which is a lavasopressin-degrading enzyme.

Treatment of excessive thirst

Treatments for problems that cause excessive thirst.

Mellitus diabetes

The treatment of excessive thirst in diabetes mellitus, is through the treatment of diabetes itself, in this way the reduction of this symptom could be achieved. It consists of improving nutrition, activity and medicines to control the level of sugar in the blood.

Diabetes insipidus

The goal of treatment is to restore body water and osmotic homeostasis avoiding complications. One of the possible alternatives is an analog of the antidiuretic hormone, desmopressin.

This substance has a more powerful and prolonged antidiuretic action, even than the hormone ADH itself. In addition, the pharmacological treatment of central diabetes insipidus has been complemented with the rational use of diuretics and the prescription of low-salt diets.

Primary polydipsia

As the cause is associated with SIADH, treatment includes regulating hyponatremia (fluid retention) and the cause of SIADH. Acute hyponatremia requires immediate treatment while chronic hyponatremia with mild symptoms must be slowly corrected. The main thing is to reduce the consumption of water and specialized medical attention.

Gestational polydipsia

The most recommended treatment is desmopressin, due to the fact that it is not degraded by vasopressinase. It is important that these people in the gestation period have a restriction of salt intake that allows them to decrease plasma volume, and thus have more ADH availability.

By Dr. Eric Jackson

Dr. Eric Jackson provides primary Internal Medicine care for men and women and treats patients with bone and mineral diseases, diabetes, heart conditions, and other chronic illnesses. He is a Washington University Bone Health Program physician and is a certified Bone Densitometrist. Dr. Avery is consistently recognized in "The Best Doctors in America" list.

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