Hypothyroidism

Dogs Hypothyroidism occurs when the body makes inadequate levels of thyroid hormone; it is a common endocrine disorder in middle-aged and older dogs. In dogs, it appears to occur spontaneously. Cats In cats, as a naturally occurring disease, hypothyroidism is very rare. It most commonly occurs in association with I131 treatment for hyperthyroidism when some cats can become hypothyroid after receiving the radioactive iodide. Predisposed Breeds Certain breeds such as Dobermans, Golden Retrievers, Labrador retrievers, Great Danes, poodles and Boxers seem predisposed to hypothyroidism. Clinical signs This hormone controls overall body metabolism. The signs can be subtle, at first- a general slowing down, lethargy, exercise intolerance, fatigue or weight gain (not associated with increased appetite or food intake). Skin problems are common- hair loss (not associated with itchiness), poor hair growth (or slow re-growth in clipped areas, following surgery) and changes in the coat- dullness, dryness, scaling and coarseness and recurrent skin infections. Neuromuscular problems are common also- overall weakness and stiffness with movement, muscle atrophy, weakness of facial muscles to result in a "sad" face and occasionally, a dilated esophagus that can be associated with regurgitation and aspiration pneumonia. Diagnosis The diagnosis is based on a blood test, specifically a T4 level, that is a measurement of circulating thyroid hormone levels. However, sometimes there are other conditions of the body that will make the T4 levels appear lower than they really are. A more specific and sensitive test, a free T4 by equilibrium dialysis, can help to diagnose those dogs that are truly hypothyroid. Other changes often seen on the accompanying blood panel are a mild anemia and an elevation in cholesterol levels. Treatment Treatment consists of thyroid supplement in the form of levothyroxine (Synthyroid, Soloxine, Thyro-tabs) given 1-2 times a day. Prognosis The future of a dog or cat with hypothyroidism is excellent and as long as they continue to receive thyroid supplementation, they have very good quality lives. Monitoring It is important to check the T4 levels to make sure the dog is on the appropriate dose. This is usually done 3-4 weeks after starting the medication. This is a timed test and the test must done 4-6 hours post pilling. After starting with supplementation, you should notice a change in your dog- usually increased energy and the ability to move with more ease. Improvement in the coat and weight loss in overweight individuals may take longer to show. Long term care Based on the results of the T4 test, you may need to increase or decrease the dose and return again within a month after the adjustment for another T4 test. If a dog is well-regulated, a recheck of T4 levels is recommended every 6-12 months, depending on how the dog is doing. When scheduling T4 tests with our office, please remember that this blood test must be done 4-6 hours post-pilling, whether the medication is given 1 or 2 times a day. If you have any questions regarding this disease and its treatment, don't hesitate to contact your veterinarian. The above is general veterinary information. Do not begin any course of treatment without consulting your regular veterinarian. All animals should be examined at least once every 12 months.