Sulphatoxy melatonin: an index of depression in anorexia nervosa and bulimia nervosa.

Urinary excretion of the principal melatonin metabolite, sulphatoxy melatonin (aMT6s), was assessed both during the day and during the night in 38 female eating disorder patients (anorexia nervosa, n = 17; bulimia nervosa, n = 12; anorexia nervosa + bulimia nervosa, n = 9) and 14 female control subjects. Correlations between nocturnal serum melatonin and urinary aMT6s were also obtained. All patient groups and the controls showed a preservation of diurnal rhythm with elevated nocturnal urinary aMT6s values and no significant difference in amplitude between groups. However, patients with concurrent major depression had significantly lower levels of daytime and nighttime urinary aMT6s than the nondepressed group. Weight did not influence these findings. Correlations between nocturnal serum melatonin levels and urinary aMT6s were high for control subjects (r = 0.77) and moderate for the patient groups (r = 0.31). This may reflect differences in the rate of excretion of melatonin between patients and controls.