Hypothyroidism is characterized by atrophy or malfunction of the thyroid gland. Clinical symptoms include obesity, lethargy, and/or coat problems. Affected animals may also have various reproductive problems including irregular or absent heat cycle and lack of fertility in both male and female. Diagnosis of hypothyroidism is by laboratory tests measuring levels of T3 and T4 (produced by the thyroid gland) in the blood. Treatment consists of daily administration of oral thyroid supplement. When treated successfully the prognosis is excellent and the dog’s lifespan is normal. Lifelong thyroid supplementation may be required. Many clinically normal, healthy Golden’s may test slightly under the accepted range of “normal” T3 and T4 levels and it is quite possible that the normal values for this breed may be slightly lower than the values used for the general canine population. There are some dogs that will have epileptic attacks when hypothyroid and stop seizuring when put on thyroid. While there is a link, the hypothyroid condition does not cause epilepsy, and the dog should still be monitored for epilepsy.