Posterior Pituitary Flashcards
where is ADH produced?
supraoptic* and paraventricular nuclei of the anterior hypothalamus
where is ADH released?
posterior pituitary
to what kind of receptor does ADH bind to regulate serum osmolarity?
V2 receptors
where does ADH cause aquaporin channels to be inserted into?
principal cells of the renal collecting duct
primary and secondary regulation of ADH
primary: osmoreceptors in hypothalamus
secondary: hypovolemia
SIADH: pathogenesis
excessive release of ADH from the posterior pituitary causing excessive free water retention –> hyponatremia, urine osmolality > serum osmolality
SIADH: consequences of severe hyponatremia
cerebral edema, seizures
what drug can cause SIADH?
cyclophosphamide (chemo)
what cancer can cause ectopic ADH to be released, causing SIADH?
small cell lung cancer
cardinal feature of SIADH
euvolemic hyponatremia
what measurements are low in SIADH?
serum sodium and serum osmolality
treatment for SIADH (4)
fluid restriction, IV hypertonic saline, conivaptan and tolvaptan (ADH receptor (V2) antagonists), demeclocyline (tetracycline antibiotic used as ADH antagonist)
why is it important to correct SIADH slowly?
osmotic demyelination syndrome: rapid resolution of sodium levels can cause water to leave brain cells too quickly, leading to osmotic shrinkage that results in severe damage to the myelin sheath of axons
diabetes insipidus: pathogenesis
characterized by intense thirst and polyuria with inability to concentrate urine due to lack of ADH (central) or renal resistance to ADH activity (nephrogenic)
what is central (neurogenic) diabetes insipidus and what are some etiologies?
deficient production/release of ADH; autoimmune, trauma, surgery, ischemic encephalopathy, pituitary tumors
