Endotoxn-induced nonthyroidal illness in dogs.
OBJECTIVE
To determine the effects of endotoxin administration on thyroid function test results and serum tumor necrosis factor-alpha (TNF-alpha) activity in healthy dogs.


METHODS
6 healthy adult male dogs.


METHODS
Serum concentrations of thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3'5'-triiodothyronine (rT3), free T4 (fT4), and endogenous canine thyroid stimulating hormone (TSH), and TNF-alpha activity were measured before (day-1; baseline), during (days 0 to 3), and after (days 4 to 24) IV administration of endotoxin every 12 hours for 84 hours.


RESULTS
Compared with baseline values, serum T3 concentration decreased significantly, whereas rT3 concentration increased significantly 8 hours after initial endotoxin administration. Serum T4 concentration decreased significantly at 8 and 12 hours after initiating endotoxin administration. Serum T4 concentration returned to reference range limits, then decreased significantly on days 6 to 12 and 16 to 20. Serum fT4 concentration increased significantly at 12, 24, and 48 hours after cessation of endotoxin treatment, compared with baseline values. Serum rT3 concentration returned to reference range, then decreased significantly days 5 and 7 after stopping endotoxin treatment. Serum TNF-alpha activity was significantly increased only 4 hours after initial endotoxin treatment, compared with baseline activity.


CONCLUSIONS
Endotoxin administration modeled alterations in thyroid function test results found in dogs with spontaneous nonthyroidal illness syndrome. A decrease in serum T4 andT3 concentrations and increase in serum rT3 concentration indicate impaired secretion and metabolism of thyroid hormones. The persistent decrease in serum T4 concentration indicates that caution should be used in interpreting serum T4 concentrations after resolution of an illness in dogs.
Panciera
David L
DL
Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA.
Ritchey
Jerry W
JW
Ward
Daniel L
DL
D000818:Animals; D004283:Dog Diseases / Q000097:blood / Q000139:chemically induced* / Q000503:physiopathology*; D004285:Dogs; D004731:Endotoxins / Q000494:pharmacology*; D008297:Male; D013959:Thyroid Diseases / Q000097:blood / Q000139:chemically induced* / Q000503:physiopathology / Q000662:veterinary*; D013960:Thyroid Function Tests / Q000662:veterinary; D013961:Thyroid Gland / Q000187:drug effects* / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014285:Triiodothyronine, Reverse / Q000097:blood; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D004731:Endotoxins; D014409:Tumor Necrosis Factor-alpha; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013972:Thyrotropin; D013974:Thyroxine