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Endocrine Abstracts (2024) 99 P435 | DOI: 10.1530/endoabs.99.P435

1Lille University Hospital, Department of Endocrinology, Diabetology and Metabolism, Lille, France; 2Lille University Hospital, Include – INtegration Center of the Lille University hospital for Data Exploration, Lille, France; 3Lille University hospital, Department of statistics and data management, Lille, France; 4Lille University Hospital, Biology Department, Lille, France


Introduction: Guidelines recommend using first-line tests, including 24-hour urine-free cortisol (UFC), overnight 1-mg dexamethasone suppression test (DST), and late-night salivary cortisol (LNSC) for the positive diagnosis of hypercortisolism. Unfortunately, LNSC access is constrained in certain institutions, requiring, as an alternative, hospitalization for midnight plasmatic cortisol (F00h) measurement. This study explores the diagnostic potential of afternoon plasma cortisol (F16h), aligning with the contemporary shift toward outpatient care.

Materials and methods: Patients assessed for suspicion of Cushing’s syndrome at a single center from September 2017 to Jully 2021. Plasma cortisol at 8h (F8h), 16h (F16h), and midnight (F00h), DST, and UFC performed in a single center were extracted via the Integration Center of the Lille University Hospital for Data Exploration. Two endocrinologists reviewed electronic patient’s medical files to establish the positive diagnosis of CS. Patients with interfering treatment, including oestrogen therapy, and patients assessed for adrenal incidentalomas or recurrence of Cushing’s disease were excluded.

Results: Among 1922 cortisol cycles, 589 patients (41.3% women, mean age 50.7±16.30 years) were included, with 49 (8.3%) diagnosed with CS. There were no significant differences between age and sex between patients with CS (CS group) and patients without CS (no-CS group). The F00h, F16h, 24h-UFC and DST were significantly higher in the CS group compared to the no-CS group (F00h: 8.60 μg/dl [5.60–11.50] vs 2.65 μg/dl [1.70 to 4.10], P<0.001; F16h: 10.80 μg/dl [8.40–14] vs 6.40 μg/dl [4.70–8.60], P<0.001; UFC: 71 μg/24h [38.4–116] vs 30 μg/24h [21–45], P<0.001; DST: 4.4 μg/dl [3 to 9.3] vs 1 μg/dl[1–1.3], P<0.001). F16h significantly correlated with DST, 24h-UFC and F00h in both groups, with a stronger correlation in the CS group. The area under the ROC curve (AUC) for the F16h did not differ from UFC yet its sensitivity was higher using the optimal diagnostic threshold. The AUC for the F16h was significantly lower than that for F00h and DST. The optimal cut-off of the F16h was 7.9 μg/dl, achieving 83.7% sensitivity and 67.4% specificity.

Discussion: If LNSC should remain the first-line test for evaluating the circadian rhythm of cortisol, when not available, the F16h could be an interesting alternative for diagnosing hypercortisolism in an ambulatory setting. Further studies are required to assess its variability and confirm its utility in different situations, with a specific focus on evaluating recurrences of Cushing’s disease.

Volume 99

26th European Congress of Endocrinology

Stockholm, Sweden
11 May 2024 - 14 May 2024

European Society of Endocrinology 

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