The melatonin status of patients in end-stage chronic renal failure (CRF) was evaluated by the determination of daytime plasma melatonin levels and by the investigation of the circadian rhythmicity of melatonin secretion. A significant increase in plasma melatonin concentration was found in all CRF patient groups investigated, i.e. CRF patients on conservative treatment (CT; n = 48), CRF patients on maintenance haemodialysis treatment (HD; n = 39) and CRF patients on peritoneal dialysis (PD; n = 32). Successful transplantation led to a marked reduction in plasma melatonin levels. The circadian rhythm of melatonin secretion would appear to be suppressed in CRF as the nocturnal secretory surge was absent in all HD patients and in 80% of the posttransplantation patients studied.

Daytime plasma melatonin values were measured by radioimmune assay in 86 patients with breast cancer; 280 assays were done and compared with the clinical status of the patients. Patients in the advanced disease group had significantly higher levels than those in the adjuvant treatment group, and patients with progressive disease had significantly higher values than those in remission or with stable disease. No significant differences were found between different dominant metastatic disease sites. Multiple-regression tests showed a significant inverse correlation between survival and melatonin values.