We have reported tissue distribution studies in rats and dogs with a new adrenal imaging agent. 131I-6beta-iodomethyl-19-nor-cholesterol (NP-59). This agent concentrated five times higher in the adrenal cortex than 131I-19-iodocholesterol without increased concentration in non-adrenal tissues. We now report in 34 patients, the findings on scintigraphy with NP-59 compared with angiograms and/or adrenal vein hormone levels and histopathology, including 13 patients with hypercortisolism, 12 with primary aldosteronism, 2 with low renin hypertension, 5 with catecholamine excess, 1 with a liver metastasis from an aldosterone producing adrenal cortical carcinoma, and 1 with anaplastic adrenal cortical carcinoma. NP-59 adrenal cortical uptake was more rapid and intense and background activity was less prominent, allowing earlier and more definite interpretation of images than was possible with 131I-19-iodocholesterol.
The results of adrenal scintiscans, venograms and venous aldosterone levels are compared with the histologic findings in 33 patients submitted to operations for primary aldosteronism. Standard and suppression scintiscans were performed 2-14 days following intravenous administration of 2mCi of 131I-19-iodocholesterol. The adrenal lesions were histologically classified into four categories: 25 patients had adenomas, 6 had macronodular hyperplasia, 1 had microscopic hyperplasia and 1 had an adenocarcinoma. Asymmetrical uptake between the two adrenals seen on standard scintiscans did not differentiate between a tumor or asymmetrical hyperplasia, unless the tumor was greater than 2 cm in diameter. During suppression scintiscans, unilateral uptake visible within five days of tracer injection was consistent with adenoma. Patients with nodular hyperplasia demonstrated early uptake in both adrenal glands during suppression scintiscans, while the patient with microscopic hyperplasia did not. The type of adrenal lesion was correctly identified in 20/26 (77%) of patients by suppression scintiscans; 21/28 (75% of patients by venograms and 12/16 (75%) of patients who had adrenal venous aldosterone measurements attempted. The majority of surgically correctible lesions could be identified on suppression adrenal scintiscans. Adrenal vein catheterization can be reserved for those patients in whom the results of suppression scintiscans are inconsistent with the clinical degree of aldosteronism.
A new adrenal cortex imaging agent. 6β‐131 I‐iodomethyl‐19‐norcholest‐5(10)‐en‐3β‐ol (NP‐59)[I] was synthesized by the homallylic rearrangement of 19‐iodocholesterol or directly from cholest‐5‐ene‐3β, 19‐diol‐19‐toluene‐p‐sulfonate via homoallylic rearrangement with the iodide ion as a nucleophile and subsequent exchange with Na131I. NP‐59 appears to concentrate 5 times better than 19‐iodocholesterol in the rat adrenal and is currently being evaluated as a possible diagnostic agent in man.
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