REN and chronic kidney disease: (3) In 53 patients with chronic kidney disease (CKD), impaired night-time excretion of melatonin metabolite urinary 6-sulfatoxymelatonin tightly correlated with altered urinary excretion of angiotensinogen [205], previously detected as a marker of renal renin–angiotensin system activation and renal damage in CKD patients [206].