Fluid and electrolyte problems associated with diabetes insipidus and syndrome of inappropriate antidiuretic hormone.

This article has presented the complex system by which the hypothalamus regulates body fluid balance. In summary, ADH is synthesized and released via the hypothalamohypophyseal system. The supraoptic nucleus in the hypothalamus produces the ADH and the neurohypophysis stores and releases it. Osmoreceptors in the hypothalamus sense minute changes in the extracellular osmolality and stimulate or inhibit ADH synthesis and secretion. At the same time the thirst center of the hypothalamus is stimulated by the extracellular osmolality and brings conscious awareness of thirst into play. Once ADH is secreted, its target organ is the kidney, specifically the collecting ducts and distal tubules. Blood volume, blood pressure, emotional input, medications, and various pathologic conditions also affect ADH synthesis and secretion. As with any complex system there are numerous opportunities for a breakdown to occur. The most common types of pathologic conditions are the various forms of DI and SIADH. Both of these disorders have numerous causes, which must be identified prior to effective treatment. Serum and urine osmolality and sodium content are of use in diagnosing the disorders. Treatment is then geared toward correcting the underlying problem and controlling water balance, usually through pharmacologic agents. Nursing care includes meeting both the physical and psychologic needs of patients and educating them in the process of living with their transient or permanent condition.