Cushing's syndrome: comparison between Cushing's disease and adrenal Cushing's.

PURPOSE: The most common etiology of Cushing's syndrome (CS) is an ACTH-producing pituitary adenoma (pitCS), reported as 2-3 times more frequent than primary adrenal CS (adrCS). We aimed to analyze and compare features of patients with pitCS and adrCS. METHODS: A retrospective file review of 196 consecutive patients (age 46.8 ± 15.6 years, 76% female) diagnosed with CS in 2000-2017 and followed for 5.2 ± 4.2 years; 109 (55.6%) had pitCS and 76 (38.8%) adrCS. Epidemiologic, clinical and biochemical factors were compared between and within the pitCS and adrCS groups. RESULTS: The relative proportion of pitCS to adrCS (1.4) was lower than previously reported and gradually decreased during the study years to only 1.2 in 2012-2017. The most common reason for CS screening was weight-gain in the pitCS group (48.6%) and adrenal incidentaloma in the adrCS group (39.5%). The pitCS patients were diagnosed at younger age (42.5 ± 15.1 vs. 51.6 ± 15.1 years, p < 0.001) and had lower prevalence of hypertension (51.4 vs. 74%, p = 0.005). There was no between-group difference in severity of hypercortisoluria. Within the adrCS group, patients diagnosed after detection of an adrenal incidentaloma had milder hypercortisoluria than the remaining patients, presented with smaller adrenal lesions (35.9 ± 16.3 vs. 49.1 ± 33.7 cm, p = 0.04), and received post-adrenalectomy glucocorticoid treatment for shorter periods (13 ± 11.6 vs. 31 ± 40 months, p = 0.04). CONCLUSIONS: The relative proportion of adrCS to pitCS is rising, probably because of an increasing detection of cortisol-secreting adrenal incidentalomas associated with milder hypercortisolism. There is no difference between pitCS and adrCS in the severity of hypercortisoluria, although significant clinical differences were found.