Flashcards in 35. SIADH Deck (27)
causes of SIADH
1. ectopic ADH ( eg. small cell lung cancer(
2. CNS disorfer / heat trauma
3. Pulmonary disease
4. Drugs ( eg cyclophosphamide)
drug that causes SIADH
1. excessive free water retention
2. Euvolemic hyponatremia with continued urinary Na+ excretion
3. urine osm > serum osm
1. fluid restriction
2. IV hypertonic salin
3. ASH antagonists
4. salt tablets
ASH antagonists - drugs
SIADH - body respond to water retention with
decreases aldosterone , increases ANP + BNP ---> increased Na+ secretion --> normalization of extracellular fluid volume ---> euvolemic hyponatremia
SIADH - body decreases aldosterone to
maintain nerar - normal volume status
SIADH - NA+ ? ( why?)
decreased aldosterone to maintain near normal volume status
severe hyponatremia can lead to
1. cerebral edema
severe hyponatremia - correct .... ( and why)
to prevent osmotic demyelination syndrome
osmotic demyelination syndrome - also known as
central pontine myelinolysis
pegvisomant mechanism of action
GH recptor antagonist
octreotide mechanism of action
Laron syndrome - mechanism
Dwarfism : defective growth hormone receptor --> decreased linear growth
Laron syndrome - lab
Laron syndrome - clinical feature
2.small head circumference,
3.characteristic facies with saddle nose and prominent
4.delayed skeletal maturation,
Nelson syndrome - mechanism
Enlargement of existing ACTH-secreting pituitary adenoma after bilateral adrenalectomy for
refractory Cushing disease (due to removal of cortisol feedback mechanism).
Nelson syndrome - presents with
Nelson syndrome - treatment
pituitary irradiation or surgical resection
secondary causes of neprhogenic Diabetes insipidus
• A patient with COPD is found to be hyponatremic, with high urine osmolarity and low serum osmolarity. What is the likely diagnosis?
SIADH, or syndrome of inappropriate antidiuretic hormone secretion, which can be caused by lung cancer
• A patient with recently diagnosed small cell lung cancer retains fluid. How do his serum and urine osmolarities compare? Pathophysiology?
Urine > serum osmolarity; SIADH (ectopic ADH from small cell lung cancer) causes low aldosterone to maintain near-normal volume status
• A patient with hyponatremia and fluid retention has SIADH (syndrome of inappropriate antidiuretic hormone secretion). Possible causes?
Ectopic ADH production (e.g., small cell lung cancer), certain drugs (e.g., cyclophosphamide), CNS disease or head trauma, pulmonary disease
• A patient with SIADH has seizures. How could this have been prevented?
Fluid restriction, hypertonic saline, conivaptan, tolvaptan, or demeclocycline, slow hyponatremia correction to avoid osmotic demyelination
• An 80-year-old smoker with COPD gains 10 pounds in 2 days; his urine specific gravity is 1.040. What is the likely ectopic source of ADH?
Small cell lung cancer (paraneoplastic syndrome)—the patient is predisposed to this cancer because he smokes
• A patient is diagnosed with SIADH. Physical exam is negative for peripheral edema, JVD, or pulmonary edema. Why is this?
In SIADH, the body responds to water retention by decreasing aldosterone (causing hyponatremia) to maintain near-normal volume status