Relationship between Total Homocysteine, Folic Acid, and Thyroid Hormones in Hypothyroid Dogs

Abstract

BackgroundBoth elevated homocysteine and decreased folic acid concentrations are observed in human patients with hypothyroidism and can influence the development of numerous secondary disorders.ObjectivesThe aim of the study was to assess total homocysteine concentration in serum and to examine its relationship with the concentration of folic acid and thyroid hormones (tT4 and fT4).AnimalsTen healthy and 19 hypothyroid client‐owned dogs.MethodsDogs with clinical signs of hypothyroidism had the diagnosis confirmed by additional tests. Total homocysteine, folic acid, total thyroxine, and free thyroxine concentrations in serum were evaluated.ResultsHypothyroid dogs were diagnosed with increased homocysteine (median 22.20 μmol/L; range, 16.50–37.75) and decreased folic acid (median 20.62 nmol/L; range, 10.54–26.35) concentrations, as compared to healthy dogs (11.52 μmol/L; range, 10.00–16.65 and 30.68 nmol/L; range, 22.84–38.52, respectively). In sick dogs, total homocysteine was inversely correlated with folic acid (ρ = −0.47, P < 0.001), total thyroxine (ρ = −0.69, P = 0.0092), and free thyroxine (ρ = −0.56, P = 0.0302).ConclusionsHypothyroidism in dogs causes hyperhomocysteinemia. Concomitant mild folic acid decrease in hypothyroid dogs might be as a result of hyperhomocysteinemia.

Serum homocysteine concentration in dogs with immunosuppressant-responsive enteropathy

“…A decreased glomerular filtration rate has been associated with increased serum HCY in hypothyroid dogs [2]. Although, dogs with overt chronic kidney disease (CKD) were not included in the study, glomerular filtration rate was not measured.…”

“…In veterinary medicine, altered serum HCY concentrations have been reported in healthy dogs and dogs with various diseases. For instance, HCY has been reported to increase in dogs with heart and kidney disease [10] and in hypothyroid dogs [2]. The association between elevated serum HCY concentration and hypocobalaminemia has been demonstrated in Shar-Pei dogs with chronic diarrhoea [11].…”

“…Homocysteine (HCY) is an endogenous sulphur-containing amino acid, produced by the systemic conversion of methionine, which is an exogenous amino acid present in animal proteins [1,2]. HCY is a pro-inflammatory molecule and its hematic concentration is influenced by nutritional determinants, including folate (vitamin B9), cobalamin (vitamin B12), pyridoxin (vitamin B6), as well as the genetic polymorphism of enzymes involved in its metabolic pathway [1,3].…”

Review of cobalamin status and disorders of cobalamin metabolism in dogs

“…However, increased serum or plasma HCY concentrations are less specific for intracellular lack of cobalamin than is increased serum MMA concentrations . Serum HCY concentrations can also be increased with renal insufficiency or hypothyroidism …”

Cobalaminmangel bei Hund und Katze

“…Laut Autoren kann bei einer Cobalaminkonzentration < 209 ng/l im Blut von einem Mangel ausgegangen werden und eine Messung der MMA ist somit nicht erforderlich (48). Homocystein lässt sich als Diagnostikum beim familiären Cobalaminmangel des Chinese Shar Pei heranziehen (22), allerdings erst nach Ausschluss anderer Erkrankungen wie Nephropathien, Kardiopathien, Systemic Inflammatory Response Syndrome (SIRS) und Hypothyreose (19,35,36). Neben diesen in der Veterinärmedizin untersuchten Erkrankungen mit Einfluss auf die Homocysteinkonzentration wurden beim Menschen weitere korrelierende Faktoren nachgewiesen.…”