The relationship of serum lipids to adrenal-gland uptake of 6 beta-[131I]iodomethyl-19-norcholesterol in Cushing's syndrome.

An alteration in serum cholesterol levels has been suggested as a possible modifier of adrenal uptake of the cholesterol analog, 6 beta-[131I]iodomethyl-19-norcholesterol (NP-59). To assess the effect of hypercholesterolemia upon NP-59 adrenal uptake, patients with Cushing's syndrome (eight with pituitary-dependent, four with ACTH-independent, and two with ectopic-ACTH syndrome) were selected for retrospective analysis based on the availability of serum cholesterol (n = 14) and triglyceride (n = 10) concentrations obtained at the time of adrenal scintigraphy. A negative correlation (r = 0.78, p < 0.01) was found between NP-59 uptake and serum cholesterol levels in patients with pituitary-dependent Cushing's disease. Compared with pituitary-dependent disease, the ectopic-ACTH syndrome and ACTH-independent states demonstrated equal or greater adrenal uptake of NP-59 at similar serum cholesterol concentrations. Serum triglyceride concentrations did not correlate with total adrenal uptake of NP-59 in any of the patient groups studied. Increased serum cholesterol concentrations are associated with diminished adrenal uptake of NP-59, and in some cases may limit the diagnostic efficacy of adrenal scintigraphy in Cushing's syndrome.