Serotonin and melatonin secretion and metabolism in patients with liver cirrhosis

INTRODUCTION Hepatic encephalopathy is one of the symptoms of liver failure. The exact causes of encephalopathy are complex and still unclear. Apart from elevated blood ammonia levels, the role of numerous other factors is being considered.
OBJECTIVES The aim of the study was to determine the serum level of serotonin and melatonin and the urinary excretion of their metabolites (5‑hydroxyindoleacetic acid [5‑HIAA] and 6‑sulfatoxymelatonin [6‑HMS]) in patients with various stages of liver cirrhosis.
PATIENTS AND METHODS The study comprised 75 patients with alcohol‑induced liver cirrhosis and 25 healthy subjects (control group). Based on the Child‑Pugh classification, 3 groups of 25 patients each were distinguished – group A, B, and C with grade A, B, and C of liver failure, respectively. Blood samples were drawn at fasting at 9 a.m., and 24‑hour urine collection was performed. Immunoenzymatic assays were used to determine serum melatonin and serotonin levels as well as urine 5‑HIAA and 6‑HMS concentrations.
RESULTS Serum serotonin levels were 159.8 ±23.1 ng/ml in controls, 179.3 ±21.1 ng/ml in group A (P >0.05), 143.2 ±22.8 ng/ml in group B (P >0.05), and 114.5 ±37.6 ng/ml in group C (P <0.01). Serum melatonin levels were 10.6 ±1.7 in controls, 31.2 ±9.8 pg/ml in group A (P <0.01), 49.8 ±12.2 pg/ml in group B (P <0.001), and 94.8 ±22.6 pg/ml in group C (P <0.001). Urinary 5‑HIAA excretion was 5.9 ±2.1 mg/24 h in controls, 5.9 ±1.9 mg/24 h in group A (P >0.05), 4.8 ±1.2 mg/24 h in group B (P >0.05), and 4.6 ±1.4 mg/24 h in group C (P <0.05). Urinary 6‑HMS excretion was 26.6 ±15.1 μg/24 h in controls, 23.2 ±7.9 μg/24 h in group A (P >0.05), 18.3 ±10.6 μg/24 h in group B (P >0.05), and 6.5 ±3.6 μg/24 h in group C (P <0.001).
CONCLUSIONS Disturbances in serotonin and melatonin homeostasis observed in patients with liver cirrhosis may be associated with advanced encopaholopathy.