Comparison of 2 Doses of Recombinant Human Thyrotropin for Thyroid Function Testing in Healthy and Suspected Hypothyroid Dogs

Abstract

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 mg rhTSH and 18 clinically healthy dogs.Methods: All dogs were stimulated with 75 and 150 mg 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 mg 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.

The Role of Hypothyroidism in the Etiology and Progression of Dilated Cardiomyopathy in Doberman Pinschers

“…In agreement with the owners and if the dogs were not yet under treatment for hypothyroidism, a TSH‐stimulating test was performed . For this test, TT 4 was measured before and 6 hours after the administration of 150 μg/dog recombinant human TSH (thyrotropin alpha) , . The results of the TSH‐stimulation tests were interpreted according to criteria established in previously published studies .…”

“…For this test, TT 4 was measured before and 6 hours after the administration of 150 μg/dog recombinant human TSH (thyrotropin alpha) , . The results of the TSH‐stimulation tests were interpreted according to criteria established in previously published studies . Briefly, a poststimulation TT 4 concentration of >2.5 μg/dL and values being at least 1.5 times the basal TT 4 concentration were considered a normal euthyroid test result.…”

Characterization of recombinant human and bovine thyroid-stimulating hormone preparations by mass spectrometry and determination of their endotoxin content

“…Therefore, compared to bTSH, rhTSH can be regarded as a much safer product. This assumption is supported by the finding that thus far, no adverse reactions in dogs have been observed even after the repeated administration of rhTSH [5,6,9]. In selected dogs in which hypothyroidism had been suspected, we repeated the TSH stimulation test three times using rhTSH.…”

“…In selected dogs in which hypothyroidism had been suspected, we repeated the TSH stimulation test three times using rhTSH. Even though the third test was performed within 12 to 24 months after the first stimulation, no dogs had adverse reactions after the rhTSH administration [6]. …”

Effect of Recombinant Human Thyrotropin on the Uptake of Radioactive Iodine (123I) in Dogs with Thyroid Tumors

“…Results of TSH stimulation were interpreted comparing serum TT4 concentrations at baseline and 6 h after rhTSH administration. Euthyroidism was confirmed when post-stimulation TT4 was ≥40 nmol/L and hypothyroidism was considered likely when post-stimulation TT4 concentration was <20 nmol/L [13], [19]. Intermediate results (post-stimulation TT4 between 20 and 40 nmol/L) were not observed.…”