Radiochemical diagnosis of adrenal disease

The adrenal gland consists of cortical and medullary components, both of which may be functionally imaged using radiopharmaceuticals designed to take advantage of the specialized physiology of each tissue. Radiolabeled cholesterol derivatives are taken up by normal and abnormal adrenal cortex and provide an in vitro map of adrenocortical function in Cushing's Syndrome, hyperaldosteronism, and hyperadrenogenism. Quantification of uptake shows strong correlation with biochemical parameters of adrenocortical hyperfunction. In the case of incidentally discovered euadrenal masses scintigraphy may help to distinguish between benign, nonfunctional cortical adenomas, and destructive, potentially malignant lesions. Radiolabeled metaiodobenzylguanidine (MIBG) is a tracer of type I uptake and intracellular storage capacity for catecholamines in sympathomedullary tissues and tumors derived from this system. This permits the location of pheochromocytomas of all types (benign and malignant, intra- and extra-adrenal, sporadic and familial) as well as neuroblastomas in all stages. Other neuroendocrine tumors with type I uptake capacity may also be imaged. In suitable cases preliminary data suggests the administration of large doses of MIBG may permit internal radiotherapy of otherwise untreatable neuroendocrine tumors.