Iodocholesterol Adrenal Tissue Uptake and Imaging in Adrenal Neoplasms*

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Abstract
To correlate iodocholesterol tissue uptake with the ability to visualize adrenal cortical neoplasms, eight female patients with adrenal carcinoma had adrenal scintiscans after the injection of 19-[131I]iodocholesterol. Patients with cortisolsecreting carcinomas failed to image either the tumor or uninvolved adrenal tissue. In contrast, patients with androgen-secreting carcinomas (which do not suppress pituitary ACTH secretion), although still failing to image the tumor, had visible concentration of the radionuclide in the ipsilateral and contralateral adrenal glands. Slices of these tissues obtained at either surgery or postmortem examination were analyzed for iodocholesterol uptake. Results were compared with adrenal tissue obtained from patients with either cortisol- or aldosterone-secreting adenomas and patients on dexamethasone suppression. There was a strong correlation between the adrenal tissue concentration of iodocholesterol and the ability to form an image on scintiscanning. The concentration of iodocholesterol in an adenoma and a carcinoma determined in this manner was compared with their cortisol secretion during in vitro incubation.The concentration of 19-[131I]iodocholesterol and the in vitro secretion of cortisol were greater in the adenoma than in the carcinoma and corresponded with adrenal imaging in the former and lack of imaging in the latter. These data provide a quantitative assessment of the differences in radioactivity concentration required for imaging of adrenal tumors. It also demonstrates that differences in the concentration of radioactivity within adrenal carcinomas and adenomas corresponds to their ability to release cortisol in vitro.