Use of recombinant human thyroid-stimulating hormone for thyrotropin stimulation test in euthyroid dogs

The purpose of this study was to evaluate the effects of the recombinant hu man thyroid-stimulating hormone (rhTSH) on serum total thyroxine (TT4) conc entration in euthyroid dogs. Six healthy beagle dogs were used in each of t he 3 phases of this study. Phase I: thyroid-stimulating hormone response te sts were performed by using a total dose of 25 mu g, 50 mu g, and 100 mu g of rhTSH, administered intravenously. Phases II and III: thyroid-stimulatin g hormone response tests were performed by using 50 mu g of rhTSH administe red by intramuscular and subcutaneous routes, respectively. In each phase a nd following all the administered doses of rhTSH, an increase in the serum TT4 concentration was noted, although it was not always significant. For ph ase I, there was a significant increase in serum TT4 concentrations. Based on this study, 50 mu g was judged to be the optimal intravenous dose of rhT SH. For phases II and III, there was no significant increase in serum TT4 a fter the administration of rhTSH. Results of this study suggest that rhTSH could be a good substitute for bovine TSH, when used by the intravenous rou te, for the TSH stimulation test in dogs. Further studies are required to c onfirm its clinical usefulness.