Melatonin secretion and non-specific immune responses are differentially expressed in corticotropin-dependent and corticotropin-independent Cushing's syndrome

Background: This study was done to clarify the relation between melatonin secretion and the hypothalamic-pituitary-adrenal axis. Material/Methods: In this clinical study using a follow-up approach, we investigated the circadian melatonin secretion and immune parameters of patients with corticotropin-dependent (Cushing's disease) and corticotropin-independent Cushing's syndrome. Plasma hormone concentrations, interleukin 1-Β (IL-1β) and total immunoglobulin E (IgE) were determined before surgical treatment and during remission of the syndrome 1 year later. Results: Patients with Cushing's disease showed mean nocturnal and diurnal melatonin plasma values similar to those of healthy controls. Only the midday level of patients (taken at 12:00) was significantly higher in comparison to controls (35.44±19.5 pg/mL vs 17.14±3.58 pg/mL; P<0.05). In contrast, patients with corticotropin-independent Cushing's syndrome had significantly lower mean nocturnal and significantly higher mean diurnal melatonin levels (52.8±17.7 pg/mL and 59.2±28.7 pg/mL, respectively; P<0.05 and P<0.05) as compared with corresponding values for controls (101.4±43.1 pg/mL and 28.9±11.7 pg/mL, respectively). In the last group of patients, significantly higher mean IL1β and plasma IgE concentrations (3.30±1.72 pg/mL and 527.8±474.0 IU/mL, respectively) were observed compared with controls (1.43±0.95 pg/mL and 35.7±32.1 IU/mL, respectively) (P<0.05). Remission of tlie hypercortisolism in these patients resulted in restoration of circadian melatonin secretion and significant reductions in plasma IL1β and total IgE levels. Conclusions: Our results demonstrate a specific mode of melatonin secretion and different nonspecific immune responses in the 2 investigated forms of hypercortisolism, specifically, corticotropin-dependent and corticotiopin-independent Ciishing's syndrome.