I have had two of 10 greys with low thyroid. They had the full panel and the results pointed to that. They both had subtle signs like easy weigh gain.
But the question really is.... Is low thyroid normal for greyhounds or are greyhounds prone to low thyroid? (Like GSD are prone to hip dipslasia). Like it or not, there is a lot of interbreeding and low thyroid can be hereditary.
I hope the soloxine work for Jeff.