Objectives—To determine the effects of racing and
training on serum thyroxine (T4), triiodothyronine (T3),
and thyroid stimulating hormone (TSH) concentrations
Animals—9 adult racing Greyhounds.
Procedure—Serum thyroid hormone concentrations
were measured before and 5 minutes after a race in
dogs trained to race 500m twice weekly for 6 months.
Resting concentrations were measured again when
these dogs had been neutered and had not raced for
3 months. Postrace concentrations were adjusted relative
to albumin concentration to allow for effects of
hemoconcentration. Thyroid hormone concentrations
were then compared with those of clinically normal
dogs of non-Greyhound breeds.
Results—When adjusted for hemoconcentration,
total T4 concentrations increased significantly after
racing and TSH concentrations decreased; however,
there was no evidence of a change in free T4 or total
or free T3 concentrations. Resting total T4 concentrations
increased significantly when dogs had been
neutered and were not in training. There was no evidence
that training and neutering affected resting
TSH, total or free T3, or free T4 concentrations.
Resting concentrations of T3, TSH, and autoantibodies
against T4, T3, and thyroglobulin were similar to those
found in other breeds; however, resting free and total
T4 concentrations were lower than those found in
Conclusions and Clinical Relevance—Except for
total T4, thyroid hormone concentrations in
Greyhounds are affected little by sprint racing and
training. Greyhounds with low resting total and free T4
concentrations may not be hypothyroid. (Am J Vet