ABSTRACT
Isolated ACTH deficiency is an uncommon disorder, which is defined by low cortisol production with low or normal plasma ACTH levels and no other pituitary abnormalities. We report five new cases of this disorder, and summarize the clinical and hormonal features of 8 previously reported cases in Korea plus 5 new cases. 1) The clinical manifestations of isolated ACTH deficiency are variable, non-specific and similar to those seen in adrenocortical insufficiency of any cause, the age of patients ranged from 21 to 66 years old with an average age of 46 years, and the male to female ratio was 10:3. 2) Hyponatremia and hypoglycemia were commmon laboratory findings, so the presence of unexplained hyponatremia or hypoglycemia should always warrant consideration of the diagnosis of isolated ACTH deficiency. 3) 3 of 13 patients accompanied by empty sella suggesting selective destruction of pituitary ACTH producing cells. 4) ACTH response to exogenous CRH or vasopressin was not elicited in all tested cases, suggesting pituitary disorders. 5) Most patients showed dramatic response with oral predinisone. In conclusion, when there are unexplained general weakness, fatigue, weight loss, nausea, vomiting, hypoglycemia, or hyponatremia, isolated ACTH deficiency should be excluded. Immunologic and pathologic studies, and hormonal evolution with glucocorticoid treatment are needed to understand the pathogenesis of isolated ACTH deficiency.