By Dr. David Gross

I adopted my long-haired, mixed breed dog (he came from a very good neighborhood) five years ago. He has recently started to shed more than usual, has put on a lot of weight and he has a smelly discharge from both ears. What should I do?

Take this poor guy to your veterinarian as quickly as you can. There are several possible explanations for these signs but one possibility is hypothyroidism, low activity of the thyroid gland.

The thyroid gland is located in the neck and produces hormones that influence the function of many other organs in the body. In dogs, overactive thyroid glands occur only rarely and when it does is usually associated with cancer. Hypothyroidism is usually a result of inflammation or shrinkage of the thyroid gland. The condition occurs most frequently in medium to large breeds of dogs and usually doing middle age. It seems to be most common in Golden retrievers, Doberman pinchers and Irish setters but don’t ask me why this is, because I have no idea.

The most common signs associated with this condition are loss or thinning of the fur, a dull hair coat, excess shedding, scaling of the skin, lethargy, and cold sensitivity. The hair loss seems to affect mostly the body of the dog, with the head and legs less affected. Excessive itchiness is usually not reported but the skin may become thickened, and develop increased pigmentation particularly where the front and rear legs rub against the body.

Hypothyroid dogs frequently suffer from ear infections with resulting pain and foul odor. Some hypothyroid dogs develop skin infections that are itchy and can result in scabby sores. Some dogs with this condition accumulate mucopolysaccharides, particularly in the muscles of the face. The result is that the affected muscles lose tone, droop and the dog develops a tragic facial expression. The cartoon character “Satchel” in Darby Conley’s comic strip “Get Fuzzy” looks to be a likely candidate for this condition; just one man’s opinion.

In a small number of afflicted dogs, the disease can result in dilation of the esophagus, known as megaesophagus. This condition results in frequent regurgitation of undigested food. Another rare sign is a neuropathy (nerve malfunction) that can result in weakness and abnormal gait

To confirm the diagnosis of hypothyroidism it is necessary to do a panel of several blood tests. The results of these tests can be influenced by other, non-thyroid, diseases so your veterinarian must sift through all the available evidence including her or his complete physical examination of your dog to make this diagnosis.

Treatment is not complicated. It involves giving your dog thyroid tablets by mouth, usually twice a day, but for the rest of his life. Once the hair coat begins to return to normal, the dosage can be reduced to once a day for some dogs.

There are two forms of thyroid hormone produced by the thyroid gland, T3 and T4. Normal animals, including humans, convert T4 to T3. Since most hypothyroid dogs who are given T4 will convert it to T3, we usually prescribe levothyroxine or L-thyroxine, the T4 form. Rarely a dog will not be able to do the conversion and will require medication with a T3 product. It is not a bad idea for your veterinarian to monitor T4 blood levels to fine tune the dosage.

If your dog has an ear infection, this needs to be treated appropriately at the same time. It usually takes about four to six weeks for hair to grow back and for the dog to return to his normal friendly happy self.

Dr. David Gross graduated from Colorado State University’s veterinary school in 1960 and was in private practice for 10 years. He enrolled in graduate school at Ohio State University earning a M.Sc. degree in 1972 and a Ph.D. degree in 1974. He retired in 2006 as Professor and Head of Veterinary Biosciences, at the University of Illinois, Urbana-Champaign. Dr. Gross is a Fellow of the Cardiovascular Section of the American Physiological Society. During his academic career, he published over 90 papers in refereed scientific journals and over 100 abstracts in proceedings of scientific meetings.