Comparison of 19-lodocholesterol and 6-lodomethylnorcholesterol as adrenal-scanning agents.

The two adrenal-specific compounds, 19-iodocholest-5-en-3beta-ol (19-iodocholesterol) and 6beta-iodometyly-19-norcholest-5(10)-en-3beta-ol (6-iodomethylnorcholesterol), synthesized pure in gram amounts have been labeled with iodine-125 and used for tissue-distribution studies in the rat. Radioactivity from 6-iodomethylnorcholesterol is accumulated in the rat adrenal gland at least 18 times more than is radioactivity from 19-iodocholesterol at 24 hr, and 50 times more at 72 hr. The use of radioactive 6-iodomethylnorcholesterol gave superior adrenal images in rats at earlier times than did radioactive 19-iodocholesterol, and the former should be equally superior when used in humans.