There are many reasons that a dog could gain weight and lose hair. First lets look at possible causes that could explain both of these symptoms. Hypothyroidism is a disease where the thyroid gland is not producing enough thyroid hormone. Dogs that are hypothyroid commonly have dull dry hair coats with hair loss starting in the tail region and gradually spreading over the body. The hair may take months to re-grow after being clipped.
Weight gain is also a common symptom.
Often dogs are brought in for exam due to their decrease in activity along with the weight gain. One of my client s complaints was that their dog could not make it around their jogging track like he could a few months before. There can be many other symptoms. These can include, increased sleeping, personality change, heat seeking, decreased fertility, slow heart rates, constipation, enlarged esophagus and other nerve dysfunction s. If your dog is showing several of these other symptoms it is likely that he has hypothyroidism.