The functional spectrum of adrenocortical adenomas

Adrenocortical adenomas (ACA) are frequently discovered at autopsy. Nowadays, modern radiologic techniques incidentally uncover the usually silent ACA during lifetime. On the basis of various reports and the results of endocrine tests, i.e. dexamethasone suppression (DST) and CRH response, we characterize 3 major types of functioning ACA. Type I ACA (cortisol < 100 nmol/l after 1 mg dexamethasone (DXM)) comprises the majority of the so-called 'nonfunctioning' adrenocortical adenomas. However, these adenomas may not be 'truly nonfunctioning' ACA, as their mean FMAX/ACTHMAX-ratio after CRH is significantly higher than in controls without ACA. Also, 19-iodocholesterol adrenal scan has shown persistent adrenal uptake despite DXM administration in some patients with normal DST. Type II ACA ('pre-Cushing's') is comparable to the euthyroid autonomous adenoma. The results of function tests suggest the existence of an ACTH-hyperresponsive subtype. Finally, type III ACA are associated with overt hypercortisolism. An ACTH-responsive and an ACTH-unresponsive form can be characterized. A continuous functional spectrum and the transition between the different types of adenomas is discussed.