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-beta (IL-1beta) 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 IL1beta 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 the hypercortisolism in these patients resulted in restoration of circadian melatonin secretion and significant reductions in plasma IL1beta 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 corticotropin-independent Cushing's syndrome.