HYPERFUNCTIONING UNILATERAL ADRENAL MACRONODULE IN 3 PATIENTS WITH CUSHINGS-DISEASE - HORMONAL AND IMAGING CHARACTERIZATION

We aimed to investigate the dynamics of adrenocorticotropin (ACTH) and cortisol secretion in pituitary-dependent Cushing's syndrome with bil ateral macronodular adrenal hyperplasia presenting as a single adrenal macronodule, and to determine the imaging characteristics of this syn drome. Three female patients were studied. Plasma ACTH and serum corti sol secretion were studied by determining their rhythmicity and pulsat ility and their responses to the administration of ovine corticotropin -releasing factor, thyrotropin-releasing hormone, metyrapone, tetracos actrin, insulin and dexamethasone. Techniques used to localize the ana tomical lesion were bilateral simultaneous inferior petrosal sinus sam pling, magnetic resonance examination of the pituitary, computed tomog raphy (CT) scanning and [Se-75]cholesterol scintigraphy of the adrenal glands. Plasma ACTH and serum cortisol levels were measured using a c ommercial radioimmunoassay and an immunoradiometric assay. The ACTH an d cortisol pulse number and amplitude were calculated using establishe d computer software. In all three patients ACTH and cortisol secretory dynamics fulfilled the requirements for diagnosis of pituitary-depend ent Cushing's syndrome. A close relationship between ACTH and cortisol pulses also favored a pituitary dependency. Study of the amplitude of cortisol pulses classified two patients in the group of hypopulsatile Cushing's disease. Adrenal CT scanning demonstrated the presence of a large single nodule. [Se-75]Cholesterol scintigraphy showed bilateral radionuclide uptake, although mostly localized over the adrenal nodul e. All patients underwent successful trans-sphenoidal hypophysectomy. Over a period of 1 year, a slow shrinkage of the adrenal nodule was ob served in two patients, while no change in volume was observed in one patient. Demonstration of an adrenal macronodule on CT scanning in pat ients with Cushing's syndrome is in itself insufficient to allow the d iagnosis of hypercorticism due to a unilateral adrenal adenoma. Additi onal dynamic endocrine testing, inferior petrosal sinus sampling and i maging techniques such as [Se-75]cholesterol scintigraphy remain neces sary to reach a correct diagnosis.