Dysregulation of plasma pro-opiomelanocortin-related peptides in neurotic depression

In order to assess whether a central hypothalamic impairment could account for the pro-opiomelanocortin (POMC)-related peptide over-secretion in depressive disorders, plasma B-lipotropin (B-LPH), B-endorphin (B-EP) and cortisol concentrations were measured in 9 patients affected by neurotic depression: a) every 4 h over a 24-h period: b) in response to insulin-induced hypoglycaemia (0.1 IU/kg body weight), and c) during dexamethasone (DXM) administration (0.5 mg X 4/day for 2 days). Eight age-matched healthy volunteers (controls) were also studied. B-EP and B-LPH were determined by specific radioimmunoassays after plasma extraction and gel chromatography. Compared with the controls, the patients showed a 3 times higher plasma B-EP, twice the normal B-LPH levels, and a 20% cortisol increase. The neurotic depressed patients showed an evening-related decrease in the levels of the 3 hormones, expressed as mean values, similar to that in the controls, whereas the single cosinor analysis revealed a significant circadian rhythm of B-LPH and B-EP only in 3 and 2 patients, respectively. Insulin-induced hypoglycaemia (ITT) stimulated the release of B-LPH and cortisol in both groups, whereas the B-EP increase was absent in the patients. DXM reduced plasma cortisol and B-LPH levels in controls and patients, but in the latter it failed to reduce the B-EP concentrations. The present data indicate that neurotic depressed patients are characterized by increased activity of the hypothalamic-pituitary-adrenal axis, with maintained circadian rhythmicity. The B-EP unresponsiveness to ITT and DXM contradicts the hormal responses of B-LPH and cortisol to the same tests and suggests a dysregulation of plasma B-EP secretion in neurotic depressed patients.