Thyrotropin-releasing hormone stimulation testing in healthy dogs.

Serum triiodothyronine (T3) and thyroxine (T4) concentrations were determined after IV administration of 200 micrograms of thyrotropin-releasing hormone (TRH) to 10 healthy euthyroid dogs. Significant (P less than 0.05) changes were not found in the T3 concentration throughout an 8-hour sampling interval. All dogs had a significant increase (P less than 0.05) in the T4 concentration at 4, 5, 6, 7, and 8 hours after TRH administration. The largest increase in the serum T4 concentration occurred 4 hours after TRH injection. From 4 to 8 hours after TRH administration, the mean increase above basal T4 concentrations was 13.9 +/- 5.4 ng/ml.