Your dog is suffering from some disease. Change its food, give it food that is rich in protein, and note the changes. May be change in food help it out. There are possibilities of hormonal disorder in your dog but in that case it should not stop eating. Find out of your dog has worms inside its intestine or stomach or had it eaten something bad from outside that has causes such an adverse effect on its secretion. Take it to vet because it needs a thorough examination.
