Effect of endotoxin on hormonal responses to thyrotropin and thyrotropin-releasing hormone in dogs.
OBJECTIVE
To determine whether administration of endotoxin affects thyroid gland function in dogs.


METHODS
24 Beagles.


METHODS
Dogs were given thyrotropin (TSH) or thyrotropin-releasing hormone (TRH) on 2 occasions. Twenty-four hours before the second challenge with TSH or TRH, all dogs were given 5 micrograms of endotoxin/kg of body weight. Serum concentrations of thyroxine (T4), free T4 (fT4), 3,3',5-triiodothyronine (T3), reverse T3, autoantibodies to T3, and plasma concentrations of ACTH and cortisol were determined.


RESULTS
Treatment with endotoxin was associated with reduced baseline concentration of serum T3 and increased baseline concentration of reverse T3 and free T4. Endotoxin treatment resulted in reduced peak serum concentration of T4 after TSH and TRH. However, peak serum concentration of fT4 after TSH and TRH were not affected by endotoxin.


CONCLUSIONS
A single dose of endotoxin affects several aspects of thyroid gland function in dogs, including T4 binding, deiodinase activity, and the thyroidal response to TSH and TRH.


CONCLUSIONS
Acute or chronic nonthyroidal illness may affect thyroid gland function in dogs. Determination of fT4 concentration may provide a means of differentiating the effects of nonthyroidal illness from those of thyroid dysfunction, because endotoxin treatment was associated with increased baseline serum free T4 concentration and unchanged peak serum fT4 concentration after administration of TSH or TRH.
Yu
A A
AA
Department of Small Animal Surgery and Medicine, Auburn University College of Veterinary Medicine, AL 36849, USA.
Kemppainen
R J
RJ
MacDonald
J M
JM
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D004285:Dogs; D004731:Endotoxins / Q000633:toxicity*; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D012044:Regression Analysis; D013961:Thyroid Gland / Q000187:drug effects / Q000502:physiology*; D013972:Thyrotropin / Q000494:pharmacology*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D013974:Thyroxine / Q000097:blood* / Q000378:metabolism; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood* / Q000378:metabolism; D014285:Triiodothyronine, Reverse / Q000097:blood / Q000378:metabolism
D004731:Endotoxins; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013973:Thyrotropin-Releasing Hormone; D000324:Adrenocorticotropic Hormone; D013972:Thyrotropin; D013974:Thyroxine; D006854:Hydrocortisone