Serum melatonin and 6-sulfatoxymelatonin in end-stage renal disease: effect of hemodialysis.

Abstract

The pineal hormone melatonin plays a role in the regulation of hypothalamic-pituitary axis, target gland function, sleep pattern, mood changes, cellular immunity, antibody response, and skin pigmentation, nearly all of which are also affected by renal insufficiency. We measured serum melatonin and its main urinary metabolite, 6-sulfatoxymelatonin (6-SM), by radioimmunoassay in 11 patients with end-stage renal disease (ESRD) between the hours of 6 and 9 a.m. during hemodialysis and again on an off-dialysis day. The results were compared with those obtained in a group of normal control subjects. Predialysis serum melatonin and 6-SM levels obtained at 6 a.m. in the ESRD patients were comparable with those obtained in the normal control group. Serum melatonin concentration in the ESRD group fell approximately 25% during dialysis while 6-SM remained virtually unchanged. The changes observed on the off-dialysis day during the same time period were of nearly the same magnitude as those seen during dialysis (-32% and 1.4%, respectively). No significant difference was found in the concentration of either analyte in the blood entering and leaving the dialyzer. These observations suggest a lack of discernible removal of either compound by hemodialysis. In contrast to the ESRD patients, who showed a slow fall in serum melatonin and no significant change in serum 6-SM on both on- and off-dialysis days, the normal control subjects showed an expected reduction in serum melatonin (-43%) and a sharp fall in serum 6-SM (-53%) between 6 and 9 a.m.(ABSTRACT TRUNCATED AT 250 WORDS)