Adipsia
A rare disorder of absent thirst due to hypothalamic or other dysfunction.
Adipsia, or hypodipsia, is a condition where a person experiences little to no sensation of thirst. This occurs when rising plasma osmolality—the concentration of dissolved substances in the blood—fails to trigger the hypothalamus to release antidiuretic hormone (ADH) to the kidneys. The body then holds onto water, and the individual loses the ability to feel thirsty. Because it is so rare, the condition has not been extensively studied.
Adipsia can appear alongside disorders like diabetes insipidus and may lead to hypernatremia. It can result from abnormalities in the hypothalamus, pituitary gland, or surrounding regions, as well as after surgery on the pituitary or hypothalamus. In some cases, hypothalamic dysfunction causing adipsia occurs without any physical lesions in the hypothalamus, though only four such instances have been reported. There are also rare psychogenic cases where patients have normal plasma osmolality and typical ADH activity.
**Cause**
**Dopamine** The neurotransmitter dopamine has been linked to feeding behavior. In one experiment, mice born without dopamine stopped eating and drinking to the point of death. When given L-DOPA, a dopamine precursor, they resumed eating. However, these mice still had the neural capacity to control feeding and drinking, suggesting dopamine is not needed to build those circuits but is instead tied to the drive for hunger and thirst. While the lack of dopamine caused adipsia in these mice, low dopamine levels do not always lead to adipsia. Additional evidence comes from studies of the nigrostriatal pathway: when this pathway is completely destroyed, animals become adipsic, aphagic, and lose their exploratory drive. Still, no research has isolated the relationship between adipsia and dopamine alone, since dopamine changes also affect eating and curiosity.
**Hypothalamus** Lesions in hypothalamic regions that regulate thirst can cause adipsia. These lesions may be congenital, acquired from trauma, or result from surgery. They create defects in the thirst-regulating center, and because the hypothalamus sits very close to ADH-related osmoreceptors, injuries there can also disrupt thirst.
**Diagnosis**
**Symptoms** Diagnosing adipsia is tricky because there are no concrete physical signs unique to it. Brain changes linked to adipsia include hyperpnea, muscle weakness, insomnia, lethargy, and, in ex
- Also known as
- Hypodipsia
- Primary cause
- Lesions or dysfunction in hypothalamic thirst-regulating regions
- Associated conditions
- Diabetes insipidus, hypernatremia
- Types
- Type A, Type B, Type C, Type D
- Key hormone involved
- Antidiuretic hormone (ADH) / vasopressin (AVP)
- Management
- Directed drinking, training, possible surgery for growths, desmopressin for diabetes insipidus, electroconvulsive therapy for psychogenic cases
Lore & Background
Adipsia may be seen in conditions such as diabetes insipidus and may result in hypernatremia. It can occur as the result of abnormalities in the hypothalamus, pituitary and corpus callosum, as well as following pituitary/hypothalamic surgery. It is possible for hypothalamic dysfunction, which may result in adipsia, to be present without physical lesions in the hypothalamus, although there are only four reported cases of this. There are also some cases of patients experiencing adipsia due to a psychiatric disease; in these rare psychogenic cases, the patients have normal levels of urine osmolality as well as typical ADH activity.
Reader's Guide
Adipsia is significant as a rare disorder that highlights the critical role of the hypothalamus and osmoreceptors in thirst regulation. Its study has revealed that dopamine is linked to the drive for hunger and thirst, though low levels of dopamine do not necessarily cause adipsia. The condition is classified into four types—Type A (essential hypernatremia syndrome), Type B (decreased vasopressin responses), Type C (complete elimination of osmoreceptors), and Type D (least common, with normal osmoregulation)—each with distinct mechanisms. Diagnosis relies on electrolyte, BUN, creatinine, serum and urine osmolality, and vasopressin levels. Management is primarily behavioral, as no medicine currently treats adipsia directly; however, surgical removal of growths on thirst centers has been successful in some cases. The disorder's legacy lies in its demonstration of the complex interplay between neurological structures and basic drives, and it underscores the need for further research given its rarity.
Did You Know?
- Adipsia can result from lesions in the hypothalamus, pituitary, or corpus callosum, as well as from pituitary/hypothalamic surgery.
- There are only four reported cases of hypothalamic dysfunction causing adipsia without physical lesions in the hypothalamus.
- In an experiment, mice born without dopamine became adipsic and would starve and dehydrate to death, but injecting L-DOPA restored eating and drinking.
- Type A adipsia (essential hypernatremia syndrome) involves an increased osmotic threshold for vasopressin release and thirst activation, with no known cause.
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