A 25-year-old woman, Mrs WG, was referred to the local endocrine clinic. She had visited her GP complaining of increasing tiredness and fatigue and, over the 4 weeks prior to presentation, had noticed she felt giddy at times, particularly when she got out of bed in the morning or on standing up from a chair. Mrs G was known to have primary hypothyroidism, on thyroxine replacement therapy and vitiligo over her forearms and chest. Her most recent set of thyroid function tests were in the normal range. The GP had noted her blood pressure to be 90/45. At the clinic the hypotension was confirmed and on questioning she had noticed increased pigmentation over her knees and around her waistband. A short Synacthen test was performed during which her basal plasma cortisol level was found to be 75 nmol/L and 100 nmol/L 30 minutes after injection of 250 |g of synthetic ACTH (Synacthen). Later her basal ACTH concentration was reported at 550 ng/L and adrenal antibodies were positive, confirming the diagnosis of primary adrenal failure. She was started on glucocorticoid replacement in the form of hydrocortisone and mineralocorticoid replacement with fludrocortisone, following which her symptoms rapidly improved.