Heather I have found the TRH Stim test on Antech Canada's website, I have attched the link.  Worth a try.

https://www.antechdiagnostics.com/country/canada/page/13/?search&dos-categories=Equine%20%26%20Large%20Animal
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Kandace K
Rocky Mountains, Alberta, Oct 2020
K and J (over the rainbow bridge) and now T
https://ecir.groups.io/g/CaseHistory/files/Kandace%20J%20and%20K
https://ecir.groups.io/g/CaseHistory/album?id=259062