This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fluid and electrolytes, Subject name: Medicine
Hyponatremia with Isovolemia is seen in- 
Select and explain. 
A. SIADH, B. Conn's syndrome, C. Cushing' syndrome, D. Frusemide therapy
A: SIADH
Answer: A: SIADH 
Explanation: The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a disorder of impaired water excretion caused by the inability to suppress the secretion of antidiuretic hormone (ADH) . If water intake exceeds the reduced urine output, the ensuing water retention leads to the development of hyponatremia Ref Davidson 23rd edition pg 366