Incidentally discovered adrenocortical adenomas are not fully nonfunctioning: immunohistochemical and dispersed adrenocortical cell study. 
To clarify the precise function of incidentally discovered adrenocortical adenoma, immunohistochemical and dispersed adrenal cell studies were performed.  We have recently seen five patients with so-called nonfunctioning adrenocortical adenoma.  Diurnal variation in plasma cortisol and suppression of plasma cortisol and urine 17-hydroxycorticosteroids in response to dexamethasone administration revealed adrenocortical function within normal limits in all cases, and no signs or symptoms of adrenal steroid hormone excess were evident.  Since a high uptake of iodomethylnorcholesterol was recognized in each adrenal mass, it was supposed that these adrenal tumors produced steroid hormone to a certain extent, and each patient received unilateral adrenalectomy.  P450c17, a key enzyme involved in cortisol production, was expressed in the tumor region in all cases in an immunohistochemical study.  Upon in vitro steroidogenesis with dispersed adrenal cells in two cases, all steroid hormones measured except for aldosterone (progesterone, 17 alpha-hydroxyprogesterone, pregnenolone, 17 alpha-hydroxypregnenolone, 11-deoxycortisol, cortisol, 11-deoxycorticosterone, corticosterone, 18-hydroxydeoxycorticosterone, dehydroepiandrosterone and androstenedione) were produced in a culture medium.  The results indicated that these tumors possessed the capacity for cortisol production, which was in agreement with the results of an iodomethyl-norcholesterol scintigraphy.  All patients with mild hypertension or diabetes mellitus had no signs or symptoms of steroid hormone excess, but they could potentially develop a steroid excess syndrome such as Cushing's syndrome in the future.