ABSTRACT
To summarize the clinical data of two cases with severe hyponatremia diagnosed as adrenal insuffiency combined with syndrome of inappropriate secret on of antidiuretic hormone(SIADH),and to review related literatures.Case 1 diagnosed as Addison's disease for 27 years and developed severe hyponatremia again but did not response well to sufficient glucocorticoid.Further examination showed SIADH caused by lung cancer and tolvaptan worked well.Case 2 was diagnosed as SIADH caused by lung cancer and responsed well to tolvaptan.However,hyponatremia reoccurred with the decreasing level of ACTH and cortisol during the chemotherapy.It was thought that hyponatremia was caused by drug-related adrenal insuffiency and glucocorticoid replacement therapy achieved good response.Both primary/secondary adrenal insuffiency and SIADH can lead to severe hyponatremia,but it is rare that the two situations exist in one patient and occur in different time.We should consider the possibility of the situations when we make differential diagnosis of refractory hyponatremia,monitoring the curative effects carefully,then correct the diagnosis timely,and reduce missed diagnosis and misdiagnosis.