Application of ACTH stimulation to adrenal imaging with radioiodocholesterol

ACTH-stimulation adrenal imaging (ACTH-I) was performed in 14 patients after baseline imaging (B-I) was performed. In six patients with no adrenal diseases in whom the findings of B-I were equivocal, morphologic normality of the adrenals was confirmed by ACTH-I because of increased adrenal uptake of radioiodocholesterol. In three patients with cortisol-producing tumors, visualization of contralateral glands by ACTH-I provided indirect evidence for autonomous cortisol secretion of the tumors. In three patients with pheochromocytoma or cyst, ACTH-I increased adjacent cortical radioactivity to more clearly delineate the lesions. In two patients with primary adrenocortical insufficiency, exogenous ACTH had no effect on adrenal uptake of the tracer. Correlation was observed between response of the adrenal net counts and urinary excretion of 17-OHCS and 17-KS. ACTH-I is useful when B-I does not provide sufficient diagnostic information or further information is needed due to low or absent radioiodocholesterol uptake by the adrenal gland(s).