Food-dependent Cushing's syndrome of long standing with mild clinical features

History and clinical findings: A 40-year-old woman complained of weight gain for 10 years. Because of this, she yearly went on a excessive weight reduction diet with weight loss of up to 12 kg. Nevertheless, a total weight gain of 15kg as well as changing degrees of hypertension, muscular weakness and severe depression were registered during this long period. For 5 years ecchymosis and for 2 years oligomenorrhoea as well as oedema had become evident. Recently large macronodular adrenal glands were found on routine abdominal ultrasound. At the time of clinical investigation early this year she presented with relatively mild Cushing features, such as moon face, central obesity, hirsutism, ecchymosis and hypertension. Investigations: Endocrine testing demonstrated suppressed plasma ACTH, low to normal plasma cortisol after overnight fasting and an inverse diurnal rhythm. During 24 hours of fasting plasma cortisol levels and free urinary cortisol excretion were within normal range, but highly elevated under normal food intake. Plasma cortisol levels increased dramatically in response to a lipid-rich meal (5.6-fold), to a protein-rich meal (6.6-fold) and to oral glucose (3.7-fold). Increases in plasma cortisol were closely correlated to increases of gastric inhibitory polypeptide (GIP) concentrations. Subcutaneous injection of octreotide completely inhibited the plasma cortisol and GIP response to oral glucose. Plasma ACTH and cortisol levels did not increase after CRH administration, but fasting plasma cortisol promptly increased after ACTH stimulation. Non-fasting plasma cortisol levels and free urinary cortisol excretion were not suppressed by high doses of dexamethasone. Abdominal computed tomography showed macronodular enlargement of both adrenal glands. Treatment and course: The patient underwent bilateral adrenalectomy. Postoperatively, she was treated with replacement doses of hydrocortisone and fludrocortisone. All Cushing features have regressed, a normal menstrual cycle and normal plasma ACTH concentrations have become evident. Conclusion: This case report not only presents a very rare cause of Cushing's syndrome - food-dependent or gastric inhibitory peptide (GIP)-dependent hypercortisolism - but it also demonstrates a special course of this disease of relatively long duration. Severe adrenal hyperplasia contrasted with mild clinical symptoms obviously caused by frequent periods of weight reduction diet. Considering this moderate clinical course it might well be that food-dependent hypercortisolism is more frequent than supposed, but not diagnosed owing to relatively mild clinical symptoms.