Evaluation of recombinant human thyroid-stimulating hormone to test thyroid function in dogs suspected of having hypothyroidism.
OBJECTIVE
To evaluate the use of recombinant human (rh) thyroid-stimulating hormone (TSH) in dogs with suspected hypothyroidism.


METHODS
64 dogs with clinical signs of hypothyroidism.


METHODS
Dogs received rhTSH (75 microg/dog, IV) at a dose independent of their body weight. Blood samples were taken before and 6 hours after rhTSH administration for determination of total serum thyroxine (T(4)) concentration. Dogs were placed into 1 of 3 groups as follows: those with normal (ie, poststimulation values indicative of euthyroidism), unchanged (ie, poststimulation values indicative of hypothyroidism; no thyroid gland stimulation), or intermediate (ie, poststimulation values between unchanged and normal values) post-TSH T(4) concentrations. Serum canine TSH (cTSH) concentration was determined in prestimulation serum (ie, before TSH administration).


RESULTS
14, 35, and 15 dogs had unchanged, normal, and intermediate post-TSH T(4) concentrations, respectively. Basal T(4) and post-TSH T(4) concentrations were significantly different among groups. On the basis of basal serum T(4) and cTSH concentrations alone, 1 euthyroid (normal post-TSH T(4), low basal T(4), and high cTSH concentrations) and 1 hypothyroid dog (unchanged post-TSH T(4) concentration and low to with-in reference range T(4) and cTSH concentrations) would have been misinterpreted as hypothyroid and euthyroid, respectively. Nine of the 15 dogs with intermediate post-TSHT(4) concentrations had received medication known to affect thyroid function prior to the test, and 2 of them had severe nonthyroidal disease.


CONCLUSIONS
The TSH-stimulation test with rhTSH is a valuable diagnostic tool to assess thyroid function in selected dogs in which a diagnosis of hypothyroidism cannot be based on basal T(4) and cTSH concentrations alone.
Boretti
Felicitas S
FS
Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
Sieber-Ruckstuhl
Nadja S
NS
Favrot
Claude
C
Lutz
Hans
H
Hofmann-Lehmann
Regina
R
Reusch
Claudia E
CE
D000818:Animals; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis / Q000662:veterinary*; D008297:Male; D011994:Recombinant Proteins / Q000008:administration & dosage; D013960:Thyroid Function Tests / Q000379:methods / Q000662:veterinary*; D013972:Thyrotropin / Q000008:administration & dosage / Q000097:blood; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors
D011994:Recombinant Proteins; D013972:Thyrotropin; D013974:Thyroxine