Performance of the Overnight 1mg Dexamethasone Suppression Test Coupled with Serum Dexamethasone Measurement in Identifying Subclinical Hypercortisolism Among Patients with an Adrenal Incidentaloma

Program: Abstracts - Orals, Poster Previews, and Posters
Session: SAT 379-412-Cushing's Syndrome
Saturday, March 7, 2015: 1:00 PM-3:00 PM
Hall D-F, Adrenal (San Diego Convention Center)

Poster Board SAT-393
Flavia A. Costa-Barbosa, Lilian F. Hayashi, Kelly C. Oliveira and Claudio E. Kater
Federal University of São Paulo, São Paulo, SP, Brazil
Introduction: The prevalence of subclinical hypercortisolism (SCH) among adrenal incidentalomas (AI) may be as high as 30%. Metabolic abnormalities (obesity, hypertension, hyperglycemia, dyslipidemia) are frequent in patients with SCH and can be corrected by surgical removal of the adenoma. Yet, both the characterization of SCH and the cutoff levels of screening tests used to classify this disorder are ill-defined. As for Cushing’s syndrome (CS), screening SCH among AI employs 24h-urinary free cortisol, late-night salivary cortisol (23hFsal), and mostly the 1mg overnight dexamethasone suppression test (1mgDST), either isolated or combined; but the likelihood of a false-positive 1mgDST is relatively high. Aim: to properly discriminate SCH among a series of patients with AI. Patients and methods: we investigated 335 consecutive patients with an AI (260F/75M, 15-87y, median: 54y) with the following procedures: 23hFsal and post-1mgDST serum and salivary cortisol. We also measured serum dexamethasone (Dex) concentration in all tests. All measurements were done by specific RIAs. Reference cutoff levels for 23hFsal (250ng/dl), pos-1mgDST serum (2.5µg/dL) and salivary cortisol (50ng/dl), and serum Dex (140ng/dL), were obtained from 164 control volunteers (108F/56M, 20-75y, median: 55y), whereas values obtained from 89 patients with proven CS (79F/10M, 15-72y, median: 41y) were used for comparison. Results: we defined SCH as the absence of Cushing’s stigmata in a patient with an AI who had a repeated post-1mgDST serum cortisol >2.5µg/dL (on validated 1mgDST, where Dex >140ng/dL) plus one elevated 23h or post-1mgDST salivary cortisol, and decreased basal ACTH or DHEAS levels. Among the 335 patients with AI, 88 (26.3%) had SCH, recognized by confirmed post-1mgDST serum cortisol >2.5 (3.9±1.5µg/dL; range 2.6-9.5µg/dL), elevated 23hFsal (in 36.1%) (316±292ng/dL; range 10-1,758ng/dL) and/or elevated post-1mgDST salivary cortisol (in 53.3%) (157±114ng/dL; range 10-491ng/dL). Decreased or suppressed ACTH and/or DHEAS were present in >70%. Patients with CS had post-1mgDST serum cortisol of 13.7±5.6µg/dL (range 2.5-35.7µg/dL) (distribution: 4% >2.5≤5; 32% >5≤10; 52% >10µg/dL). 23hFsal and post-1mgDST salivary cortisol were both high at 1,651±1,740ng/dL (range 70-6,960ng/dL) and 1,130±1,199ng/dL (range 50-6,756ng/dL), respectively. Conclusion: Based on the proposed definition, SCH was identified in a significant percentage (>26%) of patients with an AI. Validity of the 1mgDST was verified by concurrent determinations of serum Dex. As expected from a subclinical condition, post-1mgDST serum and salivary cortisol and 23hFsal values in SCH were halfway from normal controls and patients with confirmed CS. Patients so identified may benefit from surgical removal of the AI.

Nothing to Disclose: FAC, LFH, KCO, CEK

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