Hypothyroidism

DogsHypothyroidism occurs when the body makes inadequate levels ofthyroid hormone; it is a common endocrine disorder inmiddle-aged and older dogs. In dogs, it appears to occurspontaneously.CatsIn cats, as a naturally occurring disease, hypothyroidism isvery rare. It most commonly occurs in association with I131treatment for hyperthyroidism when some cats can becomehypothyroid after receiving the radioactive iodide.Predisposed BreedsCertain breeds such as Dobermans, Golden Retrievers, Labradorretrievers, Great Danes, poodles and Boxers seem predisposed tohypothyroidism.Clinical signsThis hormone controls overall body metabolism. The signs can besubtle, at first- a general slowing down, lethargy, exerciseintolerance, fatigue or weight gain (not associated withincreased appetite or food intake). Skin problems are common-hair loss (not associated with itchiness), poor hair growth (orslow re-growth in clipped areas, following surgery) and changesin the coat- dullness, dryness, scaling and coarseness andrecurrent skin infections. Neuromuscular problems are common also- overall weakness andstiffness with movement, muscle atrophy, weakness of facialmuscles to result in a "sad" face and occasionally, a dilatedesophagus that can be associated with regurgitation andaspiration pneumonia.DiagnosisThe 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 thatwill make the T4 levels appear lower than they really are. Amore specific and sensitive test, a free T4 by equilibriumdialysis, can help to diagnose those dogs that are trulyhypothyroid. Other changes often seen on the accompanying bloodpanel are a mild anemia and an elevation in cholesterol levels.TreatmentTreatment consists of thyroid supplement in the form oflevothyroxine (Synthyroid, Soloxine, Thyro-tabs) given 1-2 timesa day.PrognosisThe future of a dog or cat with hypothyroidism is excellent andas long as they continue to receive thyroid supplementation,they have very good quality lives. MonitoringIt is important to check the T4 levels to make sure the dog ison the appropriate dose. This is usually done 3-4 weeks afterstarting the medication. This is a timed test and the test mustdone 4-6 hours post pilling. After starting withsupplementation, you should notice a change in your dog- usuallyincreased energy and the ability to move with more ease.Improvement in the coat and weight loss in overweightindividuals may take longer to show.Long term careBased on the results of the T4 test, you may need to increase ordecrease the dose and return again within a month after theadjustment for another T4 test. If a dog is well-regulated, arecheck of T4 levels is recommended every 6-12 months, dependingon how the dog is doing.When scheduling T4 tests with our office, please remember thatthis blood test must be done 4-6 hours post-pilling, whether themedication is given 1 or 2 times a day. If you have any questions regarding this disease and itstreatment, don't hesitate to contact your veterinarian.The above is general veterinary information. Do not beginany course of treatment without consulting your regularveterinarian. All animals should be examined at least once every12 months.