syndrome of inappropriate ADH (SIADH)
TOO MUCH ADH secreation of high level of ADH (vasopressin) without normal physiologic stimuli for its release. (normal adreanal and thyroid function are present)
tumors associated with SIADH
tumor cells secrete ADH so cancer is associated with SIADH. small cell adenocarcinoma of the lung, carcinoma of the duodenum and pancreas, lukemia, lymphoma and Hodgkin diseasesarcoma, squamous cell carcenoma of the tongue.
Causes of SIADH
1. ectopically produced ADH from cancer tumors, 2. pituitary surgery (stored ADH is released in an unregulated fashion), 3. infectious pulmonary diseases (ADH produced ectopically by lung tissue) 4. psyciatric diseases 5. drugs that stimulate ADH (either stimulate ADH release , enhance ADH eddects, or have a biologic action similar to ADH
main features of SIADH
water retention (intoxication) that leads to hyponatremia (low blood sodium) hypoosmolirity (blood) and concentrated urine and solute loss (sodium) (hyperosmolirity)
TOO LITTLE ADH..a rare form of diabetes related to an insufficiency of ADH that leads to polyuria (dilute pee) and polydipsia (excessive thirst). two types. neurogenic form and nephrogenic form.
neurogenic form (central)
any organic lesion of the hypothalamus, pituitary stalk or posterior pituitary interferes with ADH synthesis, transport or release...type found most often, it is a complication of closed head trauma..high mortality
nephrogenic form (renal)
an acquired disorder. an insensitivity of the renal tubules to ADH (particularly the collecting tubules). related to disorders and drugs that damage the renal tubules or inhibit the generation of cAMP.
clinical manifestations of diabetes insipidus
can't concentrate urine..lots of pee...due to the absence of ADH, polyuria, nocturia, thirst, polydipsia, low urine osmolality and high-normal plasma osmolality...can develope a large bladder.
ADH or vasopressin
antidiuretic hormone..hormone secreted by the posterior pituitary gland. affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules
Diseases of the Posterior Pituitary
SIADH and diabetes insipidus...Rare....usually related to secretion of antidiuretic hormone (ADH)
clinical manifestations of SIADH
1.serum HYPOOSMOLAILITY and hypoantremia 2.urine hyperosmolarity 3. urine sodium matches sodium intake 4. normal renal, thyroid, and adrenal function. 5. absence of conditions that can alter volume status
low blood sodium in SIADH serum sodium= 140 in slight cases and 115 can cause severe problems
a measure of the total solute concentration per liter of solution