Endocrine Abstracts

Background: Benign adrenal incidentalomas (AI) are found in 3-5% of adults. All patients should undergo a 1 mg -overnight dexamethasone suppression test (1 mg -DST) to exclude cortisol excess (non-functioning adrenal tumours, NFAT; serum cortisol ≤50 nmol/l) or diagnose possible mild autonomous cortisol secretion (MACS; serum cortisol >50 nmol/l). Current guidelines discourage repeating hormonal work-up in patients with benign AI. However, data underpinning this recommendation are scarce.

Aim: To determine the proportion of AI patients who develop incident changes in 1 mg -DST results.

Methods: Retrospective single-centre study including benign AI cases with no clinical evidence of steroid excess and at least one 1 mg -DST repeated during follow-up. Patients treated with glucocorticoids or strong CYP3A4 inducers were excluded. Mann Whitney and Fisher tests were used for statistical analysis.

Results: 177 patients were included (median follow-up 21 months [range 2-44]). At baseline, 99 patients were classified as NFAT; 22 (22%) developed an abnormal 1 mg -DST during follow-up. Patients converting from NFAT to MACS had higher 1 mg -DST results at baseline (median cortisol 42 nmol/l [IQR 37-46] vs. 33 nmol/l [26-40], P < 0.001), lower DHEAS at baseline (median 1.4 μmol/l [0.8-2.1] vs. 2.2 [1.0-4.3], P = 0 .046), and lower DHEAS during follow-up than patients who remained classified as NFAT. At baseline, 78 patients were classified as MACS; 14 (18%) developed a normal 1 mg -DST during follow-up. Patients converting from MACS to NFAT had smaller adrenal tumours (median diameter 20 mm [12-26] vs. 28 [22-34]), higher baseline ACTH (median 18.8 ng/l [12.5-23.5] vs. 5.3 [2.5-10.9], P < 0.001), higher baseline DHEAS (median 2.9 μmol/l [1.9-3.2] vs. 1.0 [0.6-1.9], P = 0 .010), and higher ACTH and DHEAS during follow-up than patients with persistently abnormal 1 mg -DST.

Conclusions: 20% of patients with benign AI changed their functional status during follow-up. 1 mg -DST repetition may therefore be warranted and tumour size, 1 mg -DST, ACTH, and DHEAS results can guide this decision.