The Relationship of Adrenal Gland Iodomethylnorcholesterol Uptake to Zona Glomerulosa Function in Primary Aldosteronism*

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Abstract
Dexamethasone suppression adrenal scintiscans were performed on 37 patients referred for evaluation of primary aldosteronism (PA). Twenty-one had aldosterone-secreting adrenal adenoma (AA) and 16 had bilateral adrenal hyperplasia (BAH). The diagnosis of either AA or BAH was confirmed by adrenalectomy in 19 of 21 subjects with AA and by adrenal venous sampling in 15 of 16 patients with BAH. Biochemical parameters of PA were found in each patient while on both high (150 meq Na) and low salt (10 meq Na) intakes. Urinary aldos-terone excretion values were 49.7 ± 10.2 (±sem) μg/day (range, 11.2–103.9) and 44.2 ± 12.1 μg/day (range, 14.3-128.0) in AA patients on high and low salt intakes, respectively. In BAH patients, urinary aldosterone values were 29.1 ± 2.6 μg/day (range, 10.0–55.6) and 47.7 ± 9.0 μg/day (range, 23.0–102.0) on high and low salt intakes, respectively. A semioperator-independent computer algorithm was used to calculate adrenal gland uptake of [131I]6α-iodomethyl-19-norcholesterol (NP-59) in PA patients and in 7 patients with essential hypertension. NP-59 adrenal uptake values were 0.20 ± 0.02%/dose (range, 0.03–0.72), 0.28 ± 0.04% (range, 0.10–0.65), and 0.14 ± 0.02%/dose (range, 0.08–0.30) in AA, BAH, and essential hypertension, respectively. A significant correlation was found between adrenal gland uptake of NP-59 and urinary aldosterone excretion in AA (r = 0.93; P < 0.001) and BAH (r = 0.6; P < 0.01) patients. These data confirm that adrenal gland accumulation of NP-59 while on dexamethasone suppression can be used to characterize abnormal zona glomerulosa function in PA, in addition to localizing AA and differentiating AA from BAH.