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Serum melatonin in dogs with congenital portosystemic shunting, with and without hepatic encephalopathy
  1. Marisa da Fonseca Ferreira,
  2. Richard John Mellanby and
  3. Adam George Gow
  1. Hospital for Small Animals, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Roslin, Midlothian, UK
  1. Correspondence to Marisa da Fonseca Ferreira, Hospital for Small Animals, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Roslin, Midlothian EH25 9RG, UK; marisa.ferreira{at}


Background Melatonin is a hormone produced and secreted primarily by the pineal gland and mainly metabolised in the liver. Increased melatonin concentrations have been reported in human cirrhosis and hepatic encephalopathy (HE), a syndrome of neurological dysfunction. The pathogenesis of canine HE is incompletely understood. Melatonin has been hypothesised as a contributor to the development of HE. The aim of this study was to investigate whether serum melatonin concentrations are increased in canine congenital portosystemic shunting (cPSS), with and without HE.

Methods Medical records were retrospectively reviewed, for which archived (−80°C) serum samples were available. A canine competitive ELISA was used to measure melatonin in two cohorts: dogs with a final diagnosis of cPSS (n=23) with and without clinical signs of HE, and healthy dogs (n=15).

Results Melatonin concentrations were not significantly different (P=0.81) between healthy controls (median 27.2 pg/mL, range 19.8–161.5 pg/mL) and dogs with cPSS (median 25.7 pg/mL, range 18.5–244.9 pg/mL). Serum melatonin did not differ between cPSS patients with and without clinical signs of HE (P>0.99). No correlation was found between serum melatonin and blood ammonia (Spearman rank correlation coefficient, rs=−0.41, P=0.08).

Conclusion Serum melatonin is not increased in canine cPSS with and without HE. We found no evidence that altered melatonin metabolism plays a role in the pathogenesis of cPSS-associated HE.

  • canine
  • hepatic encephalopathy
  • ammonia
  • melatonin
  • portosystemic shunt
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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Ethics approval The Royal (Dick) School of Veterinary Studies Veterinary Ethical Review Committee (reference number 53.18).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article.

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