Presented in part at the Forum of the American College of Veterinary Internal Medicine, Seattle, June 2007. RHL is the recipient of a professorship by the Swiss National Science Foundation (PP00B-102866).
Comparison of 2 Doses of Recombinant Human Thyrotropin for Thyroid Function Testing in Healthy and Suspected Hypothyroid Dogs
Version of Record online: 26 JUN 2009
Copyright © 2009 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 23, Issue 4, pages 856–861, July/August 2009
How to Cite
Boretti, F.S., Sieber-Ruckstuhl, N.S., Wenger-Riggenbach, B., Gerber, B., Lutz, H., Hofmann-Lehmann, R. and Reusch, C.E. (2009), Comparison of 2 Doses of Recombinant Human Thyrotropin for Thyroid Function Testing in Healthy and Suspected Hypothyroid Dogs. Journal of Veterinary Internal Medicine, 23: 856–861. doi: 10.1111/j.1939-1676.2009.0336.x
- Issue online: 26 JUN 2009
- Version of Record online: 26 JUN 2009
- Submitted November 18, 2008; Revised April 30, 2009; Accepted April 30, 2009.
Background: Various protocols using different doses of recombinant human thyrotropin (rhTSH) in TSH stimulation testing have been described. However, the influence of TSH dosage on thyroxine (T4) concentration has not yet been evaluated in suspected hypothyroid dogs.
Objective: To evaluate the effectiveness of 2 doses of rhTSH.
Animals: Fifteen dogs with clinical signs consistent with hypothyroidism and abnormal stimulation results with 75 μg rhTSH and 18 clinically healthy dogs.
Methods: All dogs were stimulated with 75 and 150 μg rhTSH IV in a 1st and 2nd stimulation test, respectively. Blood samples were taken before and 6 hours after rhTSH administration for determination of total T4 concentration.
Results: Using the higher dose led to a normal test interpretation in 9 of the 15 dogs, in which stimulation had been abnormal using the lower dose. Based on follow-up information, hypothyroidism was excluded in 7 of these 9 dogs. In all 6 dogs with a blunted response to the higher dose, hypothyroidism could be confirmed. Healthy dogs showed significantly higher post-TSH T4 concentrations with the higher compared with the lower dose. Post-TSH T4 concentrations after TSH stimulation were not related to dogs' body weight in either healthy or diseased dogs.
Conclusions and Clinical Relevance: TSH dose significantly influenced test interpretation in suspected hypothyroid dogs. Differentiation between primary hypothyroidism and nonthyroidal disease was improved with 150 μg rhTSH. Because this effect was independent of the dogs' body weight, the higher dose is recommended in dogs that have concurrent disease or are receiving medication.