Great Dane Losing hair

Question
A year and a half old black Dane. Developed little pimple like growths about the size of a pencil eraser, on his back with loss of hair on those spots. Took him to the vet and they did scrapings which came back negative. Changed food to all natural meat and vegetable. Took away all rawhides. It went away and hair grew back. Now it is back with a vengeance. His whole back is almost bare and it is starting to advance to the head. Vet once again did scrapings and also did blood work for thyroid problem. His blood work came back around a 1 for his thyroid. He has become lethargic and appetite is small. He had not gained weight or grown since our last visit to the vet 2 months ago.

Answer
This is most likely a bacterial infection caused by something.  If his thyroid was only 1, then a 30 day course of a thyroid replacement tablet may help you to determine if the dog is hypothyroid.  The Great Dane is not prone to hypothyroid disease and it does not usually happen in young dogs such as yours.  So it may be something like an allergic skin dis4ease of some type or even demodex mange.  Ask your vet about these possibilities.