The concept of body fluids in the Donguibogam aligns closely with fluid metabolism in modern medicine. Beyond drinking a glass of water, fluid balance involves a complex system through which the body absorbs, transports, retains, and excretes moisture. When thirst does not resolve despite drinking water, there is a strong possibility that a problem has arisen within this delicate regulatory system.
A primary factor is osmoregulation. When salt concentration in the blood rises or blood volume drops, osmoreceptors in the hypothalamus detect the change and trigger the sensation of thirst. At the same time, the posterior pituitary gland secretes antidiuretic hormone, directing the kidneys to conserve water by concentrating urine. If this regulatory system falters, osmotic pressure cannot normalize even after drinking water, or antidiuretic hormone may fail to function properly, causing ongoing fluid loss and unremitting thirst.
Xerostomia is another central cause of persistent dry mouth. It occurs when salivary gland function drops and saliva volume decreases. Beyond general discomfort, it can contribute to dental caries, gums problems, and indigestion. Certain medications, including antihistamines, antidepressants, and diuretics, along with autoimmune conditions such as Sjögren syndrome, diabetes, thyroid gland dysfunction, radiotherapy to the head or neck, and nerve injury, can all cause xerostomia. In diabetes, elevated blood glucose causes the kidneys to excrete excess glucose through urine, pulling water along with it and producing intense thirst. This forms part of the classic triad: polyuria, polydipsia, and polyphagia.
Stress and the autonomic nervous system are also involved. Chronic stress causes hyperactivation of the sympathetic nerve, which tends to inhibit saliva production. Most people have felt their mouth go dry when nervous or stressed. While usually temporary, recurring stress can lead to ongoing dryness. Irregular dietary habits and high intake of caffeine or alcohol also disturb fluid balance and electrolyte metabolism, contributing to chronic thirst. The classical insight that body fluids fail to reach their destination mirrors modern concepts of fluid metabolism, salivary gland dysfunction, and endocrine disruption. Rather than ignoring persistent thirst, it is advisable to consult a healthcare professional to rule out underlying conditions.
