Effects of racing and nontraining on plasma thyroid hormone concentrations in sled dogs.
OBJECTIVE
To determine the effects of racing and nontraining on plasma thyroxine (T4), free thyroxine (fT4), thyroid-stimulating hormone (TSH), and thyroglobulin autoantibody (TgAA) concentrations in sled dogs and compare results with reference ranges established for dogs of other breeds.


METHODS
Cross-sectional study.


METHODS
122 sled dogs.


METHODS
Plasma thyroid hormone concentrations were measured before dogs began and after they finished or were removed from the Iditarod Trail Sled Dog Race in Alaska and approximately 3 months after the race.


RESULTS
Concentrations of T4 and fT4 before the race were less than the reference range for nonsled dogs in 26% and 18% of sled dogs, respectively. Immediately after racing, 92% of sled dogs had plasma T4 concentrations less than the reference range. Three months after the race, 25% of sled dogs had plasma T4 concentrations less than the reference range. For T4, fT4, TSH, and TgAA, significant differences were not detected in samples collected before the race versus 3 months later.


CONCLUSIONS
Plasma T4, fT4, and TSH concentrations decreased in dogs that complete a long distance sled dog race. Many clinically normal sled dogs have plasma T4 and fT4 values that are lower than the reference range for nonsled dogs. We suggest that the reference ranges for sled dogs are 5.3 to 40.3 nmol/L and 3.0 to 24.0 pmol/L for plasmaT4 and fT4 concentrations, respectively, and 8.0 to 370 mU/L for TSH.
Lee
Justine A
JA
Section of Emergency Medicine, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108, USA.
Hinchcliff
Kenneth W
KW
Piercy
Richard J
RJ
Schmidt
Karin E
KE
Nelson
Stuart
S
D000413:Alaska; D000818:Animals; D001323:Autoantibodies / Q000097:blood; D003430:Cross-Sectional Studies; D004285:Dogs / Q000097:blood*; D005260:Female; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance; D012016:Reference Values; D012420:Running / Q000502:physiology*; D013177:Sports; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D001323:Autoantibodies; D013963:Thyroid Hormones; C006606:anti-thyroglobulin; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine