SAT300 Use of Overnight Metyrapone Test In Suspected Adrenal Insufficiency: A Retrospective Single Center-Study

Abstract Disclosure: J. Saini: None. R. Gregg Garcia: None. J. Herndon: None. D.Z. Erickson: None. L. Gruber: None. I. Bancos: None. Context: Overnight metyrapone test (OMT) is a dynamic test used to diagnose secondary adrenal insufficiency (SAI). However, it is uncommonly used and the data on the OMT indications and performance are scarce. We aimed to characterize the indications, performance, and safety of outpatient OMT. Methods: Single center retrospective study in adults with OMT between April 1st, 2018 -July 31st, 2022. We evaluated three post-OMT cutoffs diagnostic of SAI: 1) 11-deoxycortisol ≤7 mcg/dL (11D≤7); 2) 11-deoxycortisol ≤10 mcg/dL (11D≤10), or 3) sum of cortisol and 11-deoxycortisol ≤15 mcg/dL (sum≤15), in comparison to pre-test probability and reference standard, defined as clinician-made diagnosis of SAI. When available, OMT-based SAI diagnosis was compared to results from the cosyntropin stimulation test (CST). Results: OMT was performed in 109 patients (76, 70% women) at a median age of 48 (IQR, 37-59) years. Pre-test probability for SAI was high in 13 (12%), moderate in 46 (43%), and low in 49 (45%) patients. Indications for OMT included evaluation of symptoms without clear SAI risk factors (38, 35%), suspected SAI due to chronic opioid use (25, 23%), pituitary pathology/therapies (25, 23%), exogenous glucocorticoid use (8, 7%), other (13, 12%). Overnight metyrapone was administered at a median dose of 2500 (IQR, 2125-3000). Adverse events were reported by 9 (8%) patients and were mild (nausea, fatigue) except for 1 patient who had to be hospitalized. The final diagnosis of SAI was made in 25 (48%) patients: 92%, 52%, and 12% of patients with high, moderate, and low pre-test probability. When compared to the clinician-made SAI diagnosis, OMT-based diagnosis of SAI was made in 60% of patients using the 11D≤7 cutoff, and in 81% of patients using the other cutoffs (11D≤10 or sum≤15). In 50 patients with concomitant CST, the final diagnosis of SAI was made in 23 (46%) patients, despite the normal CST results (post-cosyntropin peak cortisol ≥18 mcg/dL) in 12/23 patients. In patients with post-cosyntropin peak cortisol ≥18 mcg/dL, OMT was abnormal in 14% of patients (using post-OMT cutoff 11D≤7), 29% of patients (based on cutoff 11D≤10), and in 30% of patients (based on sum≤15). Conclusions: Outpatient OMT is well tolerated and was mostly used in patients with low/moderate pre-test probability for SAI. In patients with normal CST, OMT may diagnose SAI in additional 30% of patients, especially if the pre-test probability is high. Post-OMT sum of 11-deoxycortisol and cortisol <15 mcg/dL performs well in diagnosing SAI while allowing confirmation of adequate cortisol suppression. Presentation: Saturday, June 17, 2023