By: Fielding D. O'Niell, DVM, MS
One of the most common glandular diseases in dogs is caused by a decrease in thyroid hormone levels. This is the opposite of hyperthyroidism in cats and is usually caused by an auto-immune attack on the patient's own thyroid glands.
While any breed can be affected, hypothyroidism is more commonly reported in Dobermans, Golden Retrievers, Great Danes and Irish Setters. It usually occurs after two years of age and the symptoms include chronic skin problems, lethargy and weight gain.
A simple blood test to measure thyroid hormone levels will identify most cases, but some hypothyroid dogs will have normal test results even after running the more sophisticated tests that have become available. This can be very frustrating especially when the patient exhibits all of the classic symptoms of hypothyroidism. In the "olden days" before accurate lab tests were available, we would treat suspected cases and watch for signs of improvement over a six week period. Sometimes I still do that today. A wise old Internist once told me, "Study the patient as much as (if not more than) the test results."
Treatment is simple and inexpensive. A synthetic thyroid hormone supplement is given orally twice daily. This is one case where generic prescriptions don't work. After six to eight weeks, a thyroid blood level needs to be checked four to six hours after the morning pill. Once thyroid levels are normal, you will have a new dog.