Diabetes Insipidus Flashcards
Q: What is diabetes insipidus (DI) and how does it differ from diabetes mellitus?
A: Diabetes insipidus (DI) is a condition characterized by the inability of the kidneys to concentrate urine due to a deficiency of antidiuretic hormone (ADH) (central DI) or a lack of response to ADH (nephrogenic DI). It differs from diabetes mellitus, which involves elevated blood glucose levels due to insulin deficiency or resistance.
Q: What are the primary symptoms of diabetes insipidus?
A: The primary symptoms of diabetes insipidus are polyuria (excessive urination) and polydipsia (excessive thirst), due to the inability of the kidneys to concentrate urine.
Q: How is central diabetes insipidus (CDI) diagnosed and differentiated from nephrogenic diabetes insipidus (NDI)?
A: Central DI is diagnosed by a water deprivation test followed by administration of desmopressin (a synthetic ADH analogue). A significant improvement in urine osmolality suggests central DI. Nephrogenic DI is diagnosed if there is no significant change in urine osmolality with desmopressin, indicating a problem with the kidneys’ response to ADH.
Q: What is the main treatment for central diabetes insipidus?
A: The main treatment for central diabetes insipidus is desmopressin, which replaces the deficient ADH and helps concentrate the urine.
Q: What are common causes of central diabetes insipidus?
A: Common causes include idiopathic factors, head trauma, tumors (e.g., pituitary adenomas), and post-surgical damage to the pituitary gland.
Q: How do lithium and demeclocycline affect diabetes insipidus?
A: Lithium and demeclocycline can induce nephrogenic diabetes insipidus by interfering with the kidneys’ ability to respond to ADH, leading to polyuria and thirst.
Q: What laboratory findings are characteristic of diabetes insipidus?
A: Laboratory findings in diabetes insipidus include low urine osmolality, low specific gravity, and high serum osmolality due to excessive loss of dilute urine and inability to concentrate urine.
Q: What is the role of a water deprivation test in the diagnosis of diabetes insipidus?
A: The water deprivation test assesses the body’s ability to concentrate urine in response to dehydration. It helps differentiate between central and nephrogenic diabetes insipidus based on the response to desmopressin administration.
