NSG 2400 Disorders of the Posterior Pituitary Gland Study guides_ Latest Fall .

NSG 2400 Disorders of the Posterior Pituitary Gland  Concept: Fluids and Electrolytes o Exemplar: Diabetes Insipidus o Exemplar: Syndrome of Inappropriate Antidiuretic Hormone  Concept: Metabolism/Regulation o Exemplar: Syndrome of Inappropriate Antidiuretic Hormone Disorders of the posterior pituitary gland (neurohypophysis) occur with deficiency or excess of the hormone vasopressin (antidiuretic hormone [ADH]). A deficiency causes diabetes insipidus, and ADH excess causes the syndrome of inappropriate antidiuretic hormone (SIADH). Both types of problems disturb fluid and electrolyte balance. Diabetes insipidus (DI) Diabetes insipidus (DI) is a water loss problem caused by either an ADH deficiency or an inability of the kidneys to respond to ADH. The result of DI is the excretion of large volumes of dilute urine because the distal kidney tubules and collecting ducts do not reabsorb water; this leads to polyuria (excessive water loss through urination), dehydration, and disturbed fluid and electrolyte balance. Electrolyte imbalances most commonly include increased serum sodium levels. Dehydration from this massive water loss increases plasma osmolarity, which stimulates the sensation of thirst. Thirst promotes increased fluid intake and aids in maintaining water homeostasis. If the thirst mechanism is poor or absent or if the person is unable to obtain water, dehydration becomes more severe and can lead to death. ADH deficiency is classified as nephrogenic, drug-related, primary, or secondary, depending on whether the problem is caused by insufficient production of ADH or an inability of the kidney to respond to the presence of ADH. Assessment Most manifestations of DI are related to dehydration. See Chart 62-5 in your book. Key manifestations are an increase in urination and excessive thirst. Ask about a history of recent surgery, head trauma, or drug use (e.g., lithium). Although increased fluid intake prevents serious volume depletion, the patient who is deprived of fluids or who cannot increase oral fluid intake may develop shock from fluid loss. Manifestations of dehydration (e.g., poor skin turgor, dry or cracked mucous membranes) may b