Thyroid would have been my first guess too. We had a rescue Bouv that came to us being hypothyroid. She would lose patches of hair at times but mostly the thyroid medicine she was on, kept it growing pretty thick. We use to get the medicine in 500 pill bottles since it was one of those things she was going to have to take all her life. It's also one of those things that medicine does take care of it just fine. Just be aware that no matter how tight you wrap the pill up or how good the food is, a Bouvier's tongue can separate it out, swallow the food and spit the pill back out. It's amazing at times how fast they swallow the food and then you notice the pill sitting there on the floor.
Mike