The incidence of endogenous Cushing's syndrome in the modern era

Epidemiological studies on the incidence of Cushing's syndrome (CS) are few and most often includes only patients with the most common form, that is Cushing's disease (CD).

To analyse the incidence of endogenous CS in an unselected cohort of patients from western Sweden between 2002 and 2017.

Medical records from patients who had received a diagnostic code for CS and adrenocortical carcinoma in the Västra Götaland County between 2002 and 2017 were reviewed. Eighty-two patients had been diagnosed with endogenous CS in the region during the study period and were included in this analysis.

Thirty-nine patients (48%) had CD, 21 (26%) had ectopic ACTH-producing tumour, 17 (21%) had a benign adrenal CS, and 5 (6%) had cortisol-producing adrenocortical carcinoma. Nine of 21 (43%) patients with ectopic CS had an ACTH-producing lung tumour, 4 had a neuroendocrine pancreas tumour, and 5 had an occult tumour. The annual incidence of endogenous CS was 3.2 cases per million/y; 1.5 for CD, 0.8 for ectopic CS, 0.7 for benign adrenal CS and 0.2 for adrenocortical carcinoma.

Approximately three new cases of endogenous CS, per one million inhabitants, were diagnosed annually between 2002 and 2017. Compared with previous reports, proportionally more patients had ectopic CS. The reason for this is unclear although increased awareness of hypercortisolism in patients with malignant tumours in the modern era is a possible explanation.