Endocrine Abstracts

Background: ACTH-secreting pituitary adenomas represent two-thirds of Cushing’s syndrome (CS), the so-called Cushing’s disease (CD). These tumors are sometimes >10 mm in maximal diameter (macro-CD), but the majority of them are <10 mm (micro-CD). The aim of this study was to compare baseline characteristics of patients with micro-CD and macro-CD.

Materials and methods: Clinical, hormonal and radiological data of 226 patients with CD were retrospectively collected (195 females, mean age 43±13 years; micro-CD n=195, macro-CD n=31) in two Italian referral centers for CS. Surgical remission was defined in case of hypocortisolism (morning serum cortisol <50 nmol/l) early after surgery and need for substitutive glucocorticoid treatment for at least 4 months. Data are presented as mean and standard error (m/SE), P<0.05 was considered significant.

Results: Basal ACTH levels were higher in patients with macro-CD (160/44 vs 60/4 ng/l, P<0.001), however basal cortisol levels were similar (645/20 vs 710/81 nmol/l), therefore ACTH-cortisol ratio was higher in macro-CD (0.21/0.03 vs 0.09/0.01, P<0.001), suggesting that macro-corticotropinomas might secrete non-functional corticotrophin, considering the increased ACTH secretion in macro-CD. Regarding dynamic tests, ACTH peak after CRH was double in micro-CD (+195/18 vs +99/17%, P<0.05), despite similar cortisol peak: we could speculate that only the normal corticotroph cells are able to generate a significant response to CRH. Response to desmopressin test and adrenal feedback to low (1 mg) or high doses (8 mg) of dexamethasone test were preserved (mean cortisol suppression 72% in both groups after 8 mg). Late night salivary cortisol, midnight serum cortisol and urinary free cortisol (normalized for upper limit of normality) were similar among two groups, as well as clinical collected data (blood pressure, glucose metabolism, lipid profile, sodium/potassium levels, gender and age). In a subset of patients (n=125) at least 2 years of follow-up were available: the surgical remission rate was similar between subjects with micro- and macro-CD.

Discussion: Patients with micro- and macro CD presents, despite their clinical similarities, have different biological and functional features, thus not affecting the outcome of neurosurgery.