To me, total lay person, Arlie doesn't really have symptoms. She has a little baldness on her butt, but that may be unrelated, and really, it's not much. My vet said that hypothyroidism is insidious though, and one side effect can be to make the dog more prone to infections. Arlie has had a chronic problem with her vulva (there's a separate, older thread on that) and he is suggesting that this tendency toward infection might be contributing to that problem. She's not particularly lethargic, and certainly not by what I understand from this board to be by greyhound standards.
I called him to get the results I posted and wrote down what I heard on the phone. No one has commented on the T42 step test - maybe I misheard him and that isn't exactly the correct name - will ask about this along with other questions your collective feedback has suggested when I speak with him on Monday.
At this point I am of two minds about what to do. On the one hand, if Arlie goes on the Soloxine and her issues (bald spots, chronically irritated vulva) resolve, we have an answer. On the other, if she starts drinking a lot and peeing a lot, then maybe the drug is making her hyperthyroid and we stop it. It doesn't sound like it is harmful to give her, not to suggest in any way that I want to over-medicate her. On the contrary, that concern is exactly why I posted in the first place.
I certainly won't move forward with the meds until I receive more details (additional report comments, what about the equilibrium dialysis, etc.) and will let you know.