Thyroidism in Cats

This is a very interesting disease of cats which we see in nearly any age group.  The thyroid glands are located in the neck on either side of the windpipe. They act like the choke throttle in a car where they control the body's metabolism. If they are inactive (hypo-thyroidism), pets are lazy, over weight, have skin problems and greasy coats.

Symptoms: Hyper-active thyroids (hyper-thyroidism) make cats act like a car all revved up- ravenous appetite, hyper-active (just like my kids), under weight, often difficult to handle (again like my kids!) and may suffer from heart failure- rapid heart rate, shortness of breath, panting. The heart thickens at the expense of chamber size. This is called Hypertrophic cardiomyopathy.

Diagnosis: By performing a simple blood test, we can diagnose affected cats and institute therapy to knock-out the thyroid hormones causing all the problems.

Prognosis for untreated cases: Left un-treated, hyper-thyroid cats run the major risk of high blood pressure and heart failure. With the rapid heart rate, the heart muscles get thicker and thicker- its a bit like a weight lifter doing extra work. This thickening happens at the expense of the chamber (ventricle) sizes, and is called Hypertrophic Cardiomyopathy (HCM).  The ventricles become smaller and smaller and as a result, can't fill up with the same volume of blood. Less blood in means less blood out of the heart, and reduced blood supply to the body and its vital organs eg kidneys, liver, heart. Not too good!

Treatment: This involves doing a trial with a drug called Neomercazole (5mg three times a day). If there are no problems (see below), owners can continue with Neomercazole or have the thyroids removed either surgically or by sue of radio-active Iodine (at a specialist veterinary centre).  Cats in heart failure receive medications to slow the heart rate down (beta blockers e.g. Inderal, or calcium channel blockers e.g. Tenormin) and sometimes drugs to remove fluid from the lungs (diuretics e.g. Lasix).   Treated cases usually see an improvement in heart function and the removal of heart drugs from the treatment regime at this stage i.e. the heart pathology is
reversible. 

Precautions with therapy: Blood test on the kidneys are performed before and 24-3 hours after starting therapy to make sure the kidneys can handle having the blood pressure dropped. In some cats, the high blood pressure form hyper-thyroidism is keeping their poorly functioning kidneys going. By "fixing" the hyper-thyroidism, these cats can go into kidney failure.