A case of Addison's disease confirmed with low dose cosyntropin stimulation test

An eighty-year-old man who had complained of skin pigmentation and weight loss was referred to our hospital. Upon physical examination, marked hyperpigmentation was found on the whole body including oral mucosa, tongue and fingernails. Endocrinological findings showed increased ACTH (126 pg/ml) and normal serum cortisol (15.4 microg/dl). First, we used a 250 microg cosyntropin stimulation test which is valid to diagnose Addison's disease, resulting in an adequate cortisol response. Second, we performed 1 microg cosyntropin stimulation test, and the cortisol response was blunted. Since the diagnosis of Addison's disease was fairly certain, he was treated with hydrocortisone 15 mg/day, and improvement of his skin pigmentation and an increase in body weight were observed. To our knowledge, this is the first report that 1 mug cosyntropin stimulation test was helpful to make diagnosis as having Addison's disease rather than the 250 microg cosyntropin stimulation test, although it is established that the 1 mug cosyntropin stimulation test is useful in secondary or relative adrenal insufficiency.