I have a 7 year old wheaten terrier who has been the absolute sweetest, loving, easy going dog ever. About 6 months ago we realized that he seemed depressed. We had him checked out and it turned out that his thyroid was not working at all. He is now on thyroid medication and his blood levels check out fine. Lately, he has been growling and showing his teeth at with myself , my husband or my children. He can go from licking my face, to growling and snipping at me. He actually bit my face one time, luckily it wasn't too bad, but did scare me and hurt. I cannot imagine where this behavior is coming from. He is so well cared for, walked, fed, brushed, hugged and kissed every day. Has anyone ever heard of this behavior happening out of the blue like this?? I am so upset.