Se-75 norcholesterol is radiopharmaceutical derivative of cholesterol, a natural precursor in the synthesis of adrenocortical steroid hormones. Se-75 is a radioactive isotope of selenium, it has half-life period of 120 days, and emits gamma-rays upon decay. Se-75 norcholesterol was used under tradename Scintadren to diagnose a wide range of adrenal pathologies, including Cushing syndrome, Cushing's disease, carcinoma, adrenal insufficiency, and phaeochromocytoma. The drug was withdrawn in the early 2000s in favor of I-131 norcholesterol.