Anomalous responses to stimulation and suppression tests in Cushing's syndrome due to a calcified adrenal adenoma.

Introduction The differential diagnosis of the various forms of Cushing's syndrome rests mainly on the response of the adrenal glands to stimulation and suppression. Usually Cushing's syndrome due to adrenal hyperplasia is suppressed by dexamethasone in sufficient doses and stimulated by ACTH and metapyrone. Tumours either benign or malignant are usually non-responsive to stimulation or suppression by these agents. Adrenal venography may also help differentiate between tumour or hyperplasia. The results of these findings are important in that they determine the management of the disease. There have been previous reports of anomalous responses to metapyrone and dexamethasone in that tumours also may show suppression or stimulation, i.e. non-autonomy. It is, however, uncommon for any cause for Cushing's syndrome to be stimulated by dexamethasone. We wish to report a patient who had Cushing's syndrome due to a proven adrenocortical adenoma which was not only stimulated by dexamethasone but was also responsive to ACTH stimulation. Another unusual feature was the presence of radiologically visible calcification in the adenoma.