Refractory dilutional syndrome is a moderately frequent condition in which many features of IADH are seen but the classic syndrome is not present. The dilutional hyponatremia of cirrhosis and congestive heart failure may sometimes be of this type, although usually other mechanisms can better account for hyponatremia, such as overuse of diuretics. However, in some cases, IADH syndrome seems to be contributory. These patients differ from those with the classic IADH syndrome in that edema is often present and the urine contains very little sodium. In other words, the main feature is water retention with dilutional hyponatremia. Treatment with sodium can be dangerous, and therapy consists of water restriction.

Reset osmostat syndrome is another syndrome involving hyponatremia without any really good explanation, although, again, IADH syndrome may contribute in part. These persons have a chronic wasting illness such as carcinomatosis or chronic malnutrition or may simply be elderly and without known disease. Serum sodium levels are mildly or moderately decreased. As a rule, affected persons do not exhibit symptoms of hyponatremia and seem to have adjusted physiologically to the lower serum level. Treatment with salt does not raise the serum values. Apparently the only cure is to improve the patient’s state of nutrition, especially the body protein, which takes considerable time and effort. This condition has also been called the “tired cell syndrome.”