Abstract
BackgroundSled dogs performing endurance races have been reported to have a high incidence of gastric erosions or ulcerations and an increased risk of gastro intestinal bleeding leading to death in some cases. In addition, these dogs also become hypothyroid during training and exercise. Canine hypothyroidism has been shown to correlate with decreased von Willebrand factor antigen and potentially increased bleeding tendency. Whether increased gastro intestinal bleeding risk is exacerbated due to changes in the hemostatic balance is unknown. The aim of this study was to investigate the hemostatic balance in sled dogs before and after exercise and in addition evaluate any correlation to thyroid status. Twenty sled dogs have been assessed in untrained and trained condition and immediately after exercise. The first sample was collected in the autumn following a resting period, and subsequently the dogs were exposed to increased intensity of training. After four months the peak of physical condition was reached and a 68 km long sled pulling exercise was performed. Samples were collected before and immediately after the exercise. Evaluated parameters were: plasma thromboelastographic (TEG) R, SP, α and MA, activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen, von Willebrand factor (vWf), D-dimer, platelet number, thyroid hormones, hematocrit and C-reactive protein (CRP).ResultsExercise induced an overall hypercoagulable state characterized by significant decreases of TEG R and SP and an increase of α, increased concentrations of plasma vWf and decreased aPTT. In addition, a proinflammatory status was seen by a significant increase of serum CRP concentrations. Thyroid status was confirmed to be hypothyroid as training and exercise induced significant decrease of thyroxin (T4), free thyroxin (fT4) and thyroxin stimulating hormone (TSH) concentrations. Fibrinogen decreased significantly and PT increased. The training-induced changes showed correlation between T4, fT4 and aPTT and correlation between TSH and fibrinogen. Exercise-induced changes showed correlation between T4 and PT.ConclusionsExercise was associated with a hypercoagulable state and an increase of vWf concentration in this group of sled dogs. Decreased thyroid hormone concentrations after training and exercise were confirmed, but were associated with increased and not decreased vWf in this group of sled dogs.
Highlights
Sled dogs performing endurance races have been reported to have a high incidence of gastric erosions or ulcerations and an increased risk of gastro intestinal bleeding leading to death in some cases
Humans with hyperthyroidism are procoagulant as evidenced by increased factor VIII, IX, von Willebrand factor, fibrinogen, and plasminogen activator inhibitor 1 (PAI-1) which can lead to increased thrombus formation [9], while humans with hypothyroidism are hypocoagulant due to decreased FVIII, vWf and fibrinogen which can lead to increased bleeding tendency [10,11,12]
A significant change in concentration of thyroid hormones T4, Free thyroxin (fT4) and thyroxin stimulating hormone (TSH) was observed to be induced both by training for 4 months and after exercise
Summary
Sled dogs performing endurance races have been reported to have a high incidence of gastric erosions or ulcerations and an increased risk of gastro intestinal bleeding leading to death in some cases. These dogs become hypothyroid during training and exercise. Another study included sled dogs performing sled-pulling activity for 6.4 km [8], and indicated platelet activation by a significant decrease in mean platelet component (MPC) [8] It is currently unknown whether moderate exercise or training affects the hemostatic properties of sled dogs in a way similar to humans. Decreased vWf antigen has been demonstrated in dogs with hypothyroidism [13], and in sled dogs decreased concentrations of thyroid hormone concentrations following training and exercise have been reported [14,15,16]
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