Just found out my 5 year old lab has a Hypothyroid. She kept gaining weight. We walk her more than any dog owner I know. We play with her constantly. We cut her food back so much. Only covers bottom of her dish. She is picky and sometimes doesn't even eat..just leaves it until night or next day. Vet wanted to put on prescription dog food. Decided to do thyroid test first. Two weeks later the test results are in. Hypothyroid. Vet says she must be on medication for the rest of her life. Tried reading on internet, but doesn't say what will happen or side effects or how long it takes. Just describes Hypothyroid. Anyone have issues like this?