A. Even if your dog tested low on thyroid hormone, it is possible that the weight loss is caused by the hormonal imbalance and by supplementing thyroid hormone this can be put back into proper balance. Apart from that there are several other causes fpor sudden weight loss and you vet may want to do more diagnostics to rule them out: Diabetes, Tapeworm infestation, Liver disease, Addison's disease, tumor (boxers , unfortunately, are prone to getting mast cell cancer which can also affect the digestive system only, or other organs, without actually showing up in the skin,.
A. Weight loss and big appetite would suggest hyperthyroidism, which is extremely rare in dogs, so i'm surprised your dog was tested for that and actually came back low!??
It sounds very odd, I would rather suspect an intestinal condition that is alerting the absorption of the food causing increased appetite and weight loss.
I strongly advice getting a second opinion about this case, the whole thing just doesn't make any sense to me.
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