In patients with an adrenal mass, hormonally active
tumors including
pheochromocytomas as well as
aldosterone- and
cortisol-secreting
adenomas need to be considered. Several studies have demonstrated that metanephrines, which are the metabolites of
catecholamines, are reliable parameters for the diagnosis of
pheochromocytoma. In patients with an adrenal mass, we found plasma metanephrines, measured by a newly available radioimmunoassay, to be highly sensitive and specific for
pheochromocytomas, with a better accuracy than any other biochemical parameter. The plasma
aldosterone concentration (PAC) to plasma
renin activity (PRA) ratio is an established screening tool for
primary hyperaldosteronism. However, determination of active
renin concentration (
ARC) in contrast to PRA may offer advantages in regard to processing and standardization. We found a PAC to
ARC ratio of >62 in patients with PAC levels>200 ng/L to be a reliable screening method for
primary hyperaldosteronism in patients with adrenal masses. The screening for
hypercortisolism relies on excess urinary
cortisol secretion, loss of the physiological feedback during
dexamethasone challenge, and loss of the circadian rhythm. Because urinary-free
cortisol may not identify subclinical
Cushing's syndrome, in which
hypercortisolism is still mild, the 1-mg
dexamethasone suppression test has been recommended in all patients with incidentally detected masses. Alternatively, late-night
cortisol levels in saliva have been found to have a high sensitivity and specificity for the diagnosis of
Cushing's syndrome. In summary, in patients with an adrenal mass, hormonally active adrenal
tumors can be excluded with high certainty using a few highly reliable biochemical parameters.