Uptake of 131I-19-cholesterol by normal and spontaneously hyperfunctioning canine adrenals

In six normal dogs the adrenals could be visualized as separate areas of radioactivity at 7--10 days after injection of 20--40 muCi 131I-iodocholesterol per kg of body weight. Image analysis revealed uptake values of 0.15--0.3% of the injected dose. In five dogs with pituitary-dependent hyperadrenocorticism the adrenals became visible at 3--5 days after injection of the radiopharmaceutical, with uptake values of 0.38--2.2%. In six dogs with hyperadrenocorticism due to adrenocortical tumor the scintigraphy contributed to the diagnosis and the presurgical localization. The uptake values were within the normal range; the tumor could be observed at 3--10 days after injection. Additional findings on adrenal asymmetry and a case of fluctuating pituitary-dependent hyperadrenocorticism are discussed.