IL6 and Hyponatremia: Classic, ectopic SIADH, IL-6-mediated SIADH, and CSW are three distinct syndromes resulting in hyponatremia and strikingly similar laboratory findings such as low Posm, inappropriately high Uosm, high Una, hypouricemia, and the absence of edema, with normal renal, adrenal, thyroid, and cardiac function.