Abstract
BackgroundThe TSH stimulation test to confirm canine hypothyroidism is commonly performed using a recombinant human TSH (rhTSH), as up to date, canine TSH is not yet commercially available. Limiting factors for the use of rhTSH are its high costs and occasional difficulties in product availability. Less expensive bovine TSH preparations (bTSH) purified from bovine pituitary glands are readily commercially available. The aim of this study was to evaluate two different bTSH products as alternative to rhTSH using mass spectrometry.ResultsMore than 50 proteins, including other pituitary hormones, bovine albumin, hemoglobin, and tissue proteins were identified in the bTSH preparations. In contrast, rhTSH proved to be a highly pure product. Significantly higher endotoxin levels could be detected in all bTSH products compared to the rhTSH.ConclusionsBoth bTSH products are crude mixtures and therefore not an acceptable alternative to rhTSH. Their use should be discouraged to prevent unintended side effects.
Highlights
The TSH stimulation test to confirm canine hypothyroidism is commonly performed using a recombinant human TSH, as up to date, canine TSH is not yet commercially available
Selected examples of Bis-Tris gels after electrophoresis and Coomassie Blue staining of bovine TSH preparations (bTSH) and recombinant human TSH (rhTSH)-loaded gels are shown in Figure 1A and 1B, respectively
In addition to bTSH, more than 50 other proteins were identified in all bTSH samples, including other pituitary hormones such as bovine prolactin, luteinizing hormone (LH), arginine vasopressin (AVP), proopiomelanocortin (POMC), growth hormone (GH), oxytocinneurophysin, and glycoprotein hormone alpha chain
Summary
The TSH stimulation test to confirm canine hypothyroidism is commonly performed using a recombinant human TSH (rhTSH), as up to date, canine TSH is not yet commercially available. Limiting factors for the use of rhTSH are its high costs and occasional difficulties in product availability. Less expensive bovine TSH preparations (bTSH) purified from bovine pituitary glands are readily commercially available. Canine TSH would be the ideal substance to perform the test, and canine recombinant TSH could successfully be synthesized, it is not yet commercially available [3,4]. The test is commonly performed using a recombinant human TSH (rhTSH) preparation [5,6,7,8]. Limiting factors are the high cost of rhTSH and the occasional difficulties in obtaining the product.
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