SIADH: + Excessive free water retention + Euvolemic hyponatremia with continued urinary Na excretion + Urine osmolality > serum osmolality
Body responds to water retention with DECREASED aldosterone and INCREASED ANP and BNP
Water retention => Less aldosterone => Less ENAC channels => Less sodium reuptake => Loss of sodium in urine
submitted by hayayah(445), 2019-05-14T15:24:57Z
This patient has small cell carcinoma. This type of cancer is associated with paraneoplastic syndromes such as: Cushing Syndrome, SIADH, or antibodies against Ca2+ channels (Lambert-Eaton) or neurons. Amplification of myc oncogenes is also common.
SIADH (Syndrome of inappropriate antidiuretic hormone secretion) is characterized by:
Body responds to water retention with aldosterone and ANP and BNP. That is what causes the increased urinary Na+ secretion which leads to normalization of extracellular fluid volume and the euvolemic hyponatremia.