Most common paraneoplastic syndrome associated with small cell lung cancer

Question 1

What is most common paraneoplastic syndrome associated with small cell lung cancer?

Answer 1

Small cell lung cancer🡪SIADH 🡪increase in total body water (due to aquaporins expressed at collecting duct)🡪high blood volume suppresses RAAS path🡪decrease in aldostereone causes decrease in sodium reabsorption, decrease in K+ excretion)🡪decreased Na+ + increased TBW🡪hyponatremia