Hypothyroidism is a condition resulting in not enough production of thyroid hormones by the thyroid gland. Symptoms are weight gain, inactivity and dull hair with excessive shedding. The condition most often occurs in dogs 4-10 years old and in medium to large breeds. Hypothyroidism is diagnosed through blood work and is treatable! The disease in an inheritable disorder of the immune system and so testing for it is one of the four health tests recommended by the Great Dane Club of America.