So, we’re stuck in between Veteran’s Day and Thanksgiving, it’s cold, and lots of people are starting to get grumpy about it being dark as soon as our day starts (it feels like.) This is the perfect time to let you know that although vets may be knowledgeable about something, they may not like it. Any vet who tells you they love treating every disease is not telling the truth. So let’s take this not-so-delightful time of year and talk about one of my not-favorite systems —endocrine!
The endocrine system is made up of glands that secrete hormones into the bloodstream. Parts of the endocrine system which may have dysfunction include the pituitary gland, the adrenal glands, the thyroid glands and the pancreas. I do like the endocrine system, and realize its importance. But when it veers off into diseases they tend to be more nebulous, expensive to treat and monitor, and harder to control than other diseases. They are simultaneously extremely important to our pets’ health and well-being, so you need to follow them closely to make sure we’re all getting it right.
As with most things, when it comes to thyroid disease, cats and dogs have opposite views. Cats tend to get hyperthyroidism while dogs get hypothyroidism. The thyroid gland is the one endocrine organ that follows directions and is on the simpler side to treat.
In hyperthyroidism, the thyroid gland becomes overactive and produces more hormone than the body requires. Signs of hyperthyroidism in cats include changes in sleep routine, increased vocalization and increased appetite with weight loss. Many people attribute these changes to aging, since hyperthyroidism is typically seen in older cats. However, these changes will happen over the course of a few months, whereas other aging changes usually take longer. Hyperthyroidism can be easily diagnosed with a blood test and successfully treated. Treatment options include pills or a pharmacy-compounded cream that is put on their ear.
There is also a long-term solution for the treatment of hyperthyroidism. Cats can be referred for radioactive iodine treatment at a specialty center. This includes a shot that targets and eradicates thyroid tissue. This is a more expensive treatment, as the cats have to be monitored in a special room (that is built to help contain excess radiation) for about a week, but the treatment is effective for the rest of their lives. So over a couple of years, the cost evens out, and the workload is far less. This is especially convenient for people with cats who are difficult to treat, with erratic schedules, or families who travel and don’t have twice-daily cat care.
It is important to treat hyperthyroidism as soon as possible. While you may not mind having a skinny, yowling cat, too much thyroid hormone begins to negatively affect both the heart and kidneys. If it is controlled early, cats are less likely to have secondary changes.
Dogs tend to have the opposite problem of too little thyroid hormone. This is usually caused by the destruction of the thyroid gland, which makes it unable to produce enough of the hormone. Signs of hypothyroidism include hair loss without itching, weight gain despite no changes in food or exercise, and a decreased activity level. Hypothyroidism can present in other ways occasionally, including increased aggression, agitation or anxiety.
Hypothyroidism is treated with thyroid supplementation and is fairly easy to control once it is diagnosed. Blood levels need to be checked in both diseases to make sure the animal is maintaining a stable level, but once a dose is established testing can be done once yearly.
The other set of endocrine disorders have to do with the adrenal gland. These are Cushing’s disease (hyperadrenocorticism) and Addison’s disease (hypoadrenocorticism). These diseases are opposites of each other functionally, but are both seen almost exclusively in dogs.
Cushing’s disease is caused by an overproduction of cortisol. It can be either a pituitary gland (brain) or adrenal issue, but both lead to the same outcome. This can lead to signs that are the same as a dog that is on steroids for a long period of time (since cortisol is the “body’s steroid”). These include increased drinking and urination, a pot-bellied appearance due to loss of abdominal muscle strength, hair loss, thinning skin and increased respiratory effort. The effects of long-term increased cortisol are detrimental to the liver. It also causes the immune system to be suppressed which leads to increased infections, especially of the bladder.
Cushing’s disease has medical options, and again the earlier it is treated the less the liver will suffer. There are two different options for treatment and your veterinarian will help decide which is best. Signs usually start to decrease in the first few weeks of treatment, but may not fully resolve for a month or so. Treatment is most effective when the liver hasn’t been compromised for long.
Addison’s disease is caused by decreased function of the adrenal glands. There are two types of Addison’s, primary and secondary. Primary Addison’s disease results from auto-immune destruction of the adrenal gland and is the most common type. Secondary Addison’s disease results from either a tumor in the pituitary gland or long-term treatment with steroids. This is an important reason that high doses of steroids aren’t an appropriate long-term treatment for most diseases. Addison’s can also rarely be caused by a reaction to the treatment for Cushing’s disease.
Addison’s disease can be very dangerous, because in stressful situations animals need internal steroids to help their body cope. When dogs don’t produce steroids and find themselves in a stressful situation (which can be anything from boarding to simple routine changes) their bodies enter a shock-like state.
Addison’s disease has many different symptoms and can be difficult to pinpoint. The most common signs include vomiting, diarrhea, lethargy. Signs can come and go, which is part of what makes it difficult to diagnose. Addison’s disease is treated with steroids and in some cases mineralocorticoids (which are also produced in the adrenal gland). Once diagnosed, Addison’s disease has excellent control and outcome, but should be monitored closely because “crashes” can be fatal.
Both Addison’s and Cushing’s are diagnosed with a blood test. A blood sample is drawn and synthetic cortisol is then injected. A second blood sample is drawn to determine if the body’s response is appropriate. This is the same test for both diseases, as one will have abnormally high results and the other abnormally low.
Your veterinarian can discuss any specifics with you, as endocrine diseases can be complicated. Every case has things that make it individual, and should be diagnosed in conjunction with a complete exam. Most of these diseases begin to affect animals as they age, but Addison’s can occur in younger dogs, especially if large doses of steroids are being used. Thyroid disease is very common in both cats and dogs, but is controlled easily with medication allowing them to live a long and healthy life.