Role of adrenal gland scintigraphy in patients with subclinical hypercortisolism and incidentally discovered adrenal mass

Background: The role of adrenal scintigraphy (AS) in the diagnosis of subclinical hypercortisolism (SH) in adrenal incidentaloma (AI) is debated. Aim: To evaluate the possible role of AS in identifying SH in AI patients. Subjects and methods: In the retrospective phase (2000–2004), 102 AI patients [71 females (F)/31 males (M)] referred to our center were reevaluated for SH. In the prospective phase (2005–2006), 42 patients (32F/10M) with suspected SH were evaluated performing AS and biochemical assessment of cortisol secretion. We report data of the prospective phase of the study. In these patients AS was performed at baseline; the difference between the uptake of the affected and the controlateral gland [mean Δ uptake (MΔu)] was calculated. Cortisol secretion was evaluated in 3 different occasions. Patients were considered affected with SH if they presented at least twice 2 of the following criteria: urinary free cortisol >193 nmol/l, cortisol after 1 mg dexamethasone suppression test >83 nmol/l, ACTH levels <2.2 pmol/l. Results: MΔu was higher in patients with SH (no.=27, 5/22 M/F) than in patients without SH (83.7±12.5 vs 54.7±24.1%, p<0.001), and directly correlated with UFC (β=0.387, p=0.015) and was predictive of SH (odds ratio 1.12, 95% confidence interval 1.03-1.22, p=0.009) regardless of age, body mass index, and diameter of the mass. A 75% MΔu cut-off has 86.7% specificity and 81.5% sensitivity in diagnosing SH. Conclusions: AS is not recommended as screening test in AI patients, but it can be useful to exclude the presence of a subtle cortisol excess in patients with unclear biochemical diagnosis of SH.