Patients with
end-stage renal disease (
ESRD) suffer from a number of related disorders. These include endocrine abnormalities, sleep disturbances, and depression.
Melatonin is involved in the synchronization of exogenous zeitgebers with the endogenous rhythms, and it has effects on various psychological factors. As the concentrations of
melatonin and the effects of dialysis have only occasionally been investigated in
ESRD, we performed a study involving 35 patients, measuring the serum concentrations of
melatonin, and of its major metabolite
6-sulfatoxymelatonin (aMT6s), before and after
hemodialysis. Serum samples taken during morning hours from a control group (n=11) with intact kidneys served as controls. Patients were dialyzed for approximately 4 hr between 07:00 and 13:00 hr (S1), between 13:00 and 20:00 hr (S2), or between 18:30 and 22:30 hr (S3). Mean
melatonin concentrations before
hemodialysis were highly elevated when compared with the controls (40.6 vs. 6.7 pg/mL; P<0.001). Although
melatonin levels were decreased to 20.3 pg/mL after dialysis, they were still well above the control levels. Likewise, aMT6s concentrations before dialysis were highly elevated in
ESRD patients before dialysis when compared with controls (39.5 vs. 2.0 pg/mL; P<0.001), and also decreased by dialysis to levels still well above control levels (25.3 pg/mL). Clearance efficacy was better for
melatonin (48.9%) than for aMT6s (36.6%; P<0.05). In
ESRD patients, a diurnal rhythm for
melatonin was observed (S1, 45.1 pg/mL; S2, 31.5 pg/mL; S3, 48.7 pg/mL; P<0.05), indicating that the normal synthesis rhythm is maintained. None of the following secondary disorders were correlated with
melatonin concentrations:
insomnia, delayed sleep onset, night-time arousals, and
restless-leg syndrome. The reason for this observation is probably the
melatonin concentrations, which were so high that no sub-classification could be identified. It is concluded that in
ESRD patients,
hemodialysis is unable to decrease elevated levels of
melatonin and aMT6s to normal values. It is speculated that some of the secondary disorders in
ESRD are caused by supraphysiological concentrations of
melatonin.