In the overnight dexamethasone suppression test, 1.0 mg loading is superior to 0.5 mg loading for diagnosing subclinical adrenal Cushing’s syndrome based on plasma dexamethasone levels determined using liquid chromatography-tandem mass spectrometry

[摘要] The low-dose dexamethasone suppression test (DST) is one of the commonly used initial tests for endogenous Cushing’s syndrome (CS).However, there are two loading dose regimens (0.5-mg and 1-mg), which may cause some confusion in daily practice in Japan; furthermore, there are no reports regarding whether 0.5-mg DST is a better loading dose for detecting adrenal subclinical CS (SCS) based on the plasma dexamethasone (DEX) levels.Therefore, the aims of this study were (a) to develop a novel assay to measure DEX by using liquid chromatography tandem-mass spectrometry (LC-MS/MS) and (b) to compare between the 0.5-mg and 1-mg DST for SCS diagnosis based on the DEX levels.The study retrospectively analyzed 52 consecutive subjects hospitalized for diagnosis of adrenal incidentaloma but who did not exhibit an overt CS phenotype; eight (15.4%) patients were affected with adrenal SCS.Inter-individual variability of DEX levels after the DST was high, but intra-individual variability was low.DEX levels after 1-mg loading in each patient was around two times higher than those after 0.5-mg loading (ρ = 0.853 and p < 0.001).There were 45 (86.5%) and 17 (32.7%) subjects with DEX levels ≤2.2 ng/mL after the 0.5-mg and 1-mg DST, respectively (p < 0.001).Twenty-eight (93.3%) of 30 subjects and four (21.1%) of 19 subjects with detectable ACTH levels after the 0.5-mg and 1.0-mg DST, respectively, did not exhibit DEX levels >2.2 ng/mL.These results clearly indicate that the 1-mg DST is superior to 0.5-mg loading for the diagnosis of adrenal SCS.

[学科分类] 内分泌与代谢学

[关键词] Dexamethasone suppression test;Plasma dexamethasone concentration;Liquid chromatography tandem-mass spectrometry;Adrenal subclinical Cushing’s syndrome