Thirst

A constant desire to drink, often associated with oropharyngeal dryness (xerostomia), mediated by hypothalamic osmoreceptors and volume/pressure receptors responding to increased plasma osmolality or decreased effective circulating volume.

Causes

• Fluid loss and volume depletion

  • Dehydration

  • Hemorrhage

  • Excessive sweating

  • Vomiting or diarrhea

• Dietary and medication-related causes

  • High salt intake --> hypernatremia --> increased plasma osmolality

  • Diuretics

  • Anticholinergic medications: Antihistamines, antipsychotics

• Endocrine and metabolic causes

  • Diabetes mellitus

  • Diabetes insipidus

  • Hypercalcemia

  • Pregnancy

• Organ failure and systemic causes

  • Renal failure

  • Liver failure

  • Heart failure

• Psychogenic polydipsia

• Xerostomia from reduced salivary gland function