[A case of Addison's disease which became worse during interferon therapy: insulin secretion under hyposmolarity]

We report a patient with Addison's disease whose clinical features became worse during interferon therapy for chronically active hepatitis C. A 47-year-old male was admitted because somnolence developed during a 4 week treatment with interferon-alpha-2a (IFN: 900 x 104U/day). Serum Na level was 113mEq/l and plasma osmolarity was lowered to 238mOsm/kg on admission. Plasma ACTH level was high, while serum cortisol, urinary 17-OHCS and 17-KS excretion were far below the normal levels. On admission, serum prolactin, insulin levels and urinary CPR excretion increased. Normalization of serum Na level by NaCl administration attenuated hyperinsulinemia associated with the reduction of increased CPR excretion. It was supposed that IFN administration might increase cortisol consumption and worsen hypoadrenocortinism in a patient with Addison's disease. In addition, the present case raised the possibility that hyposmolarity may induce a hyperinsulinemic state in humans.