For simply ages I've been worried about my dogs health.  You will know who you are because you said it could be thyroid.  My vet was doubtlful because it doesn't show until dogs are 4 years old.  I wrote down exactly what you posted and insisted that the blood test was done.  Result came back today and I think she said hypo-thyroid.  I'll have to google that later on but it was important I said thank you first of all.

pleased you have sorted her out or at least a step towards. hypo is underactive ( same as me and loads of other people ) Now you can work on getting it under control, it can take a while to get the meds balanced so don't worry if it seems to be taking time although dog sdo seem to respond quite quickly. DR jean dodds is an auortity on thyroid so worth googling her and learning more

Fantastic!  And please, next time you see your vet, inform him that while it is less common in young dogs, it very much can and does show before they are 4 years old.  Remy's symptoms started at 1, a friend's american cocker started at around 8 months IIRC.

Most likely she is hypo - hyper is rare in dogs (cats are the other way round).  Easily treatable but yes, it can take a little while to get the dosing right.  Keep Dr Dodds in the loop - vets often won't dose high enough, going for the least dose first.

Agree with everything nikita.said

My old Bearded Collie did well for years on Thyroxin.  No reason why it shouldn't be the same for your dog.  So glad that you have an answer.