Managing Hyperthyroidism in cats

Hyperthyroidism is the most common endocrine (hormone) disorder affecting cats. As it commonly affects senior cats, it is an important reason for regular
wellness exams and blood testing.

The thyroid gland consists of two lobes that are situated on either side of the trachea, or windpipe. The gland measures mere millmetres in size, but helps to regulate many important processes in the body.

The hypothalamus and the pituitary gland in the brain are involved in regulating the levels of thyroid hormones by secreting hormones of their own to stimulate the thyroid gland. Hyperthyroidism affects cats of both sexes equally, with cases appearing in those as young as four and as old as 22, with an average age of 13 years. The most common cause of the disease is benign hyperplasia of the thyroid gland; only 1% to 2% of cases are caused by malignant tumours. Several studies implicate dietary and environmental factors in the development of the disease. Feeding cats predominantly canned food (especially fish) and the use of cat litter increase risk. The Siamese and Himalayan breeds were found to be at a decreased risk of developing the disease. Clearly, more research needs to be done.

How can you tell if your cat may have hyperthyroidism? Owners should be monitoring the following: weight loss, increased appetite, increased thirst, diarrhea, hyperactivity, vomiting and bulky, foul-smelling feces. In 10% of cases, cats will exhibit extreme lethargy and weakness, lose weight and have a poor appetite. If your pet is exhibiting any of these signs, they should be seen by a veterinarian. On physical examination, hyperthyroid cats have a rapid heart rate (over 220 beats per minute), a heart murmur and/or a gallop rhythm and poor body condition with an unkempt appearance and thickened nails. Fortunately, diagnosing hyperthyroidism is relatively easy. In most cases, a simple blood test can detect whether hormone levels are elevated.

If left untreated, many hyperthyroid cats will waste away using up first their fat reserves then their muscle tissues. The disease will also cause thickening of the heart, due to the excessive workload placed upon it, and increased blood pressure. This in turn can lead to retinal bleeding or detachment, resulting in sudden blindness. Many untreated cats become very restless, change their sleep patterns and can become quite vocal.

There are several treatment options available for treating hyperthyroidism. The oldest involves surgical removal of the affected thyroid tissue. However, surgery alone may not be curative, and given the risks of the surgery (inadvertently removing the neighbouring parathyroid glands and damaging nerves) it has fallen out of favour among many veterinarians.

Treatment with radioactive iodine will effectively control the disease in 95% of cases, with a single treatment. An oral dose is given in a controlled treatment facility; the radioactive iodine concentrates in the thyroid gland, destroying some of the gland and thereby restoring it back to a normal state. There is no surgery, anesthesia or daily medications involved with this procedure. The biggest drawback is the initial cost, due largely to the fact that patients are required to remain in the treatment facility for a minimum of one week so their urine and feces can be collected and handled as radioactive waste.

The mainstay of treatment among most veterinarians has been the use of antithyroid medications, specifically methimazole. This drug effectively blocks the effect of circulating hormones on the body. Patients start out on an initial dose and then their thyroid levels are retested until the levels are in the normal range. Some patients will vomit or show a diminished appetite on this medication. A complete blood cell count and kidney parameters should be tested, as well. Sometimes by regulating the thyroid hormone levels we uncover an underlying kidney problem. When a cat is in a hyperthyroid
state, their heart rate and blood pressure are usually elevated, which presents more blood to the kidneys for processing. When we reverse this with treatment, we sometimes find that the kidneys were also unhealthy. Now, we have two problems to manage.

The latest treatment for hyperthyroidism is a diet formulated with ultra-low levels of iodine. It has been shown to regulate the thyroid hormone thyroxine (T4) levels in 75% of cats in four weeks; 90% have normal T4 levels by eight weeks and by 12 weeks almost all cats will have normal T4 levels. In one longer-term study, the majority of cats on this diet had normal thyroid levels after one year on the diet. Cats with mild to moderate hyperthyroidism may be more effectively controlled on this diet than those with more severe disease. To work effectively, cats cannot eat any other food including treats or, for those that spend time outdoors, mice or birds.

Hyperthyroidism, as the most commonly diagnosed hormone condition in cats, warrants vigilance on the part of every cat owner and veterinarian. Fortunately, it is treatable, with many effective options available to us, enabling our furry friends to live well into their senior years.

Dr. Dieter Kohlmaier runs Westoak Animal
Hospital in Oakville, ON.

Is your cat’s behaviour


In Canada, where more than 100,000 cats are surrendered to rescue shelters annually, an estimated 28% are given up because of behavioural problems. This amounts to tens of thousands of felines each year.

Every clinical animal behaviourist, veterinarian and humane society I speak with is deeply perturbed by this statistic, not just because of the significant welfare issue that it symbolizes, but also because many behavioural problems are in fact quite manageable, and even preventable.

This raises the question — why do so many cat owners abandon or surrender their problem cats to shelters instead of addressing their pets’ behaviour issues?

Having worked with rescue organizations for more than 25 years, various explanations come to mind. First of all, as many research studies attest, cats are generally undervalued as a companion animal and not afforded the same level of care and commitment as their canine counterparts. So, when cats start to be problems, they are more likely to be either relinquished or abandoned as strays.

Secondly, some methods purported to improve cat behaviour are either ineffective or make the cat’s behaviour worse. While the Internet provides many credible sources of information for owners in need of help, there is also a wealth of misinformation out there. Determining the difference between science-based, effective information versus unhelpful twaddle can be a challenge!

However, for most guardians, a lack of awareness of both causes and treatments is a widespread reason why owners give up too soon. Cats are often regarded as being an independent, untrainable species whose behaviour is unalterable. The contrary is actually true, however. Cat behaviour problems can be successfully and permanently modified using a variety of approaches. And, successful treatment often starts with a visit to the veterinary clinic.

When a cat’s behaviour deteriorates occasionally there can be an underlying medical component. In fact, behavioural changes are often the first signs that owners notice to indicate that their cats may be sick.

Issues related to pain, injury and disease are often to blame. So, when speaking to your veterinarian about a behavioural change, they will likely conduct a basic physical examination, blood tests and urinalysis (testing the cat’s urine for signs of disease).

Be prepared to answer lots of questions about your cat. How old are they? When did the problem start? How long has it been going on for? What changes have occurred concurrently with the behavioural change? Have you recently acquired a new pet? Changed its diet? Moved home?

This information will help your veterinarian to understand what might be causing the changes. And, if they have a specialist they like to work with, you might then be referred to a clinical behaviourist. Here are some of the most common behaviour problems in cats, and what your veterinarian might be looking for.

Cats that pee and poop on clothing, floors and furniture instead of outdoors or in the litter box cause owners a great deal of frustration. According to one U.S. study of 1,286 cats entering shelters, 43% of cats surrendered with behaviour problems were admitted for this very reason.

In some instances, problems arise because the cat doesn’t like the location of its litter box, especially if it is positioned in an area where she is frequently disturbed. Or, perhaps the tray isn’t cleaned regularly enough, or the cat can’t always access the toileting area as needed. Some cats are simply fussy about the type of litter in a litter tray, most preferring deep, sandy, unscented litters.

But, in many cases, pain and disease is a reason why cats fail to use their litter trays. The conditions that your veterinarian may test for include urinary tract and bladder infections, inflammatory bowel disease, diabetes, renal failure, incontinence, hormonal abnormalities and arthritis. These conditions can cause a variety of symptoms, including painful urination, which the cat learns to associate with being inside the litter tray, or an urgency to eliminate, meaning that the cat can’t get to the litter tray soon enough. Both scenarios can lead to your cat having accidents elsewhere. To determine what is going on, your veterinarian may want to run blood tests, check your cat’s urine and, in some instances, scans and imaging may also be necessary.

Aggression shown by cats toward family members, and sometimes toward other cats, is another common relationship buster, with 30% of owners surrendering “problem cats” citing this as a primary concern. Cat scratches and bites are highly prone to infection, and when the cat resides with children or individuals with compromised immune systems, many cats quickly find themselves abandoned.

Stressors in the home can provoke even the most placid cats into being aggressive. But, when the cat seems easily provoked, or when its personality changes suddenly for the worse, then the veterinarian will often want to investigate.

There can be a number of medical reasons that can cause cats to be particularly anxious, fearful or reactive (and subsequently aggressive). Hepatic encephalopathy (arising secondarily to liver disease), parasites (which can lead to conditions such as feline ischemic encephalopathy), lead poisoning, hyperthyroidism, epilepsy, FELV/FIV and rabies are causes that your veterinarian may consider after a thorough workup.

Meowing is a completely normal feline behaviour, but some owners are disturbed when their cats’ vocalizations become loud or prolonged, and especially when they disturb the owner from sleep! Some cats are naturally very chatty, but when the nature of their dialogue changes significantly, then the veterinarian will again want to explore possible underlying medical reasons for this.

The most common reasons for excessive vocalization in cats, particularly elderly felines, include hyperthyroidism, cardiovascular conditions (particularly hypertension) and age-related cognitive decline.

While some physical tests performed in the clinic can help to identify endocrine and cardiovascular disease, age-related cognitive decline is harder to assess. Most likely, the veterinarian or a behaviourist will arrive at this diagnosis after questioning the owner in detail regarding the cat’s behavioural changes across a variety of situations.

The good news for cat owners is that most of the medical problems that can underlie house soiling, aggression and excessive vocalization are manageable. As with most health problems, the swifter the intervention, the better the prognosis.

Even though medications may lead to improvements in a cat’s behaviour (and physical health, too), other modalities are often also required to achieve the best results. Adapting your cat’s environment so that it feels safe, comfortable and calm, knowing how to read a cat’s emotions and needs through its body language and being able to handle a cat using low-stress techniques are also key to successful management.

Your veterinarian and clinical behaviourist will gladly help you deal with your concerns and give your cat the best chance of improvement.

Rebecca Ledger, BSc (Hons), MSc, PhD, FSB, is a clinical animal behaviourist and animal welfare scientist, based in Vancouver, BC. She helps cats and dogs with behavioural problems on veterinary referral across BC.;

Passing the sniff test

Cats are wondrous creatures of habit, with high standards and exacting preferences when it comes to hygiene. That’s why it’s so important to choose the right litter for your feline friend, and one that meets your needs, as well!

That said, there are many product choices out there, each with their own unique advantage.

Plain clay-based litters help contain waste by drying it. These products come in relatively large particles and are often very dusty. While they are highly absorbent, they must be fully replaced when the litter box is regularly cleaned out, rather than simply topped up. They also often use odour-control ingredients to keep the surrounding area smelling clean. Long-hair breeds sometimes prefer plain clay-based litter over newer clumping products because the coarser particles are less likely to stick to their fur. Conversely, a cat who has recently been surgically declawed may display an aversion to hard clay, as it can be painful to scratch in.

This type of litter — probably the most common type — collects cat urine into easily scoopable clumps, and many people find it can be more user friendly to cats given its finer texture versus plain clay. Only the feces and clumps need to be removed at the time of cleaning, rather than replacing the box’s entire contents. The box can then be topped up with more litter. Since they are also made of clay, clumping litters can be dusty — some brands more so than others. Many clumping litters are sold in covered pails, which can be lined with plastic bags and used as handy waste bins near the litter box for scooped clumps and feces.

One of the more recent innovations in litter has been crystal litter, made of highly absorbent silica gel and sand. The granules are tiny beads, which remain dry because liquid evaporates quickly off of them.

While the beads or pearls deal with moisture and absorb odour, they do not clump. However, with convenience in mind, some products are designed to contain urine for up to one month before the box is changed. Solid waste needs to be cleaned out more frequently.

The selection of natural plant-based litters has been growing in recent years. Their advantages include being generally dust free and environmentally friendlier than non-decomposing clays. Plant-based litters can be made from wheat, corn kernels, corncob flakes, cedar flakes or chips, kenaf (a fibre plant from the West Indies), hardwood sawdust or pine pellets. Some of these products can be flushable, depending on the type of septic system in
your home.

Another advantage of plant-based litters is that they are usually digestible, in case a curious kitten takes a bite or two. However, no matter which litter is being used, kittens should be monitored so they do not eat any of it. Plant-based products are less likely to cause them problems, but no litter is appropriate for ingestion.

Similar in almost every way to plant based products, there are now also litters made from recycled paper, including newspapers. The paper is ground, shredded or pelletized into an appropriate particle .

Given the choice, most cats will pick an open (uncovered) litter box, filled with clean unscented litter. If you have a covered box, it is especially important to be diligent about cleaning it, since any odours are confined to a small area. This may deter your cat from using the box. In addition, a covered box may not allow a larger cat enough room to scratch and dig. Both of these issues may result in your cat choosing another area (for example, your bath mat, which will certainly be quickly cleaned!) for its daily eliminations.
— By Rosalyn J. MacDonald, DVM 

Most cats are very particular about the cleanliness of their litter boxes. Some cats even prefer to urinate in one box and defecate in another, and so you may be well off to provide two boxes. In multi-cat households, some cats will not eliminate in a box used by another cat. Multi-cat households should have at least one box per cat, plus one extra, to meet their needs. It is paramount that your cat’s box be kept as clean as possible — remember that cats have a much stronger sense of smell then we do!
— By Kristina Cooper, RVT

Understanding Hairballs

When cats are not sleeping or eating, they are grooming! All that hair goes down into the digestive tract, and in the stomach, can ball up into a hairball. Usually they are long and tubular when you find them on the floor since they take that shape as they come back up the esophagus.

Some cats seem to form lots of hairballs, others bring them up rarely or never. Long haired, thick-coated cats, such as the Persian, are more likely to build them up due to the sheer volume of their hair they take in. If the cat hunts mice, the hair also can contribute to hairballs.

Usually the hairballs do not cause problems and passes through the digestive tract to be incorporated into the bowel movements. Sometimes if they get large, the cat may have trouble bringing them up or passing the hair down and stomach irritation can result. Very rarely, hairballs can become large and hard, and need surgical removal.

Daily grooming removes a lot of dead hair so that less is ingested by the cat during self-grooming. If the cat is sensitive to fleas or other external parasites, over grooming may occur and increase hair intake, so make sure these parasites are eliminated.

Keep the haircoat in good health by feeding high-quality food. Some manufacturers make a hairball preventive diet. Sometimes omega fatty acid supplements are used to increase haircoat quality and skin health. Hairball remedies, such as petrolatum-based pastes, can be given at home by mouth. These often have extra vitamins added. Avoid administering plain mineral oil — cats cannot taste it and can inhale it and get pneumonia. As well, avoid plain petroleum jelly or vegetable oil since it does not have extra vitamins added to make up for the tendency for the petroleum to interfere with fat-soluble vitamin absorption.

Though cats can safely pass hair through the digestive tract, if your cat is having any signs of ill health, including vomiting, lethargy, reduced appetite or hard, small or scant feces, contact your veterinarian. Vomiting hairballs once or twice a month is not cause for concern, but if more frequent, discuss this with your veterinarian.

Cat Scratch Disease

Cat scratch disease (CSD), also known as cat scratch fever, is a bacterial infection in humans that is can occur when a bite or scratch from a cat breaks skin and introduces a bacteria called Bartonella henselae into the tissue. This bacteria may also be introduced to an open wound if licked by a cat that has the bacteria in their saliva.

According to the U.S. Centers for Disease Control and Prevention (CDC), “CSD is caused by a bacterium called Bartonella henselae. About 40% of cats carry B. henselae at some time in their lives, although most cats with this infection show NO signs of illness. Kittens younger than one year are more likely to have B. henselae infection and to spread the germ to people. Kittens are also more likely to scratch and bite while they play and learn how to attack prey.”

Although most cats with this bateria do not show any signs of infection, humans that are infected through exposure from their cat may notice the following symptoms develop up to two weeks after exposure:
• Swelling around the wound that may be hot and painful;
• Swelling and pain in lymph nodes near wound;
• Red, raised and sometimes pus-filled lesions;
• Headache;
• Fever;
• Fatigue;
• Loss of appetite; and
• In rare cases: muscle pain, encephalitis and eye infection.

In cats, treatment may involve a long course of antibiotics, but this is usually only the case if the cat is actually symptomatic of infection, which is rare. If you have a concern that your cat may have a bartonella infection you should seek the advice of your veterinary healthcare team. If you suspect that you may have contracted CSD from a cat, it is important to seek medical attention from your family physician. Depending on the severity of the case, you may require a treatment of antibiotics based on your individual case. According the the CDC, most cases of disease resolve on their own without antibiotic treatment.

Cats can acquire this bacteria when they are bitten by fleas that carry the bacteria, or when flea dirt (feces) enters a wound. Cats are self groomers and may inadvertently ingest the bacteria or get it stuck under their nails. Your veterinary healthcare team can offer you advice on a flea prevention treatment that can help to reduce risk. Transmission to cats is also possible if an infected cat bites or scratches another cat and passes the bacteria along. Supervising your cat and preventing their ability to interact with other cats, if it may result in bites or scratches, is ideal. This includes keeping cats indoors to prevent interaction with stray cats. When it comes to those people who may be immune compromised, it is important that their interaction with certain cats, such as those that are more rambunctious (kittens) or have a tendency to bite and scratch, are limited to prevent the spread of infection.

Kristina Cooper is a Registered Veterinary Technician (RVT) and proud member of the Ontario Association of Veterinary Technicians (OAVT). She has previously worked in both small animal practice and a municipal animal shelter. With a special interest in the relationship between animal and human health, she is currently the Provincial Manager of the OAVT Public Health Rabies Response Program and an active One Health Initiative advocate. She can be reached by email at

Feline Leukemia Virus


Feline leukemia virus (FeLV) is an agent that spreads easily between cats and has potentially lethal effects, causing a variety of secondary diseases that range from secondary infections to cancer. Dr. Stanley Rubin, a veterinarian who specializes in internal medicine at the University of Illinois Veterinary Teaching Hospital in Urbana, says that FeLV is most common in outdoor male cats between the ages of one and six years old. However, kittens are at the greatest risk of infection because they do not have a fully developed immune system.

“The overall prevalence of FeLV has decreased as cat owners’ awareness of the infection has increased and steps have been taken to control the disease, such as removing cats that are FeLV positive and restricting cats to indoor lifestyles,” Dr. Rubin says. Careful monitoring and the routine use of FeLV vaccines may also be helpful.

FeLV is transmitted between cats by prolonged close contact with saliva and nasal secretions, or by sharing common water or food sources. Sometimes it can be transmitted through bites or from moms to kittens via milk, or before the kittens are born. The virus does not survive long outside a cat’s body, however. Dr. Rubin says there is no risk of cats transmitting FeLV to humans. “Numerous facts suggest that human infection is not possible,” Dr. Rubin assures.

Initially, the virus enters a cat’s bloodstream and starts to multiply. Sometimes the cat’s immune system is strong enough to fight off the infection at this stage. If not, the virus eventually travels to the bone marrow, which is where some of the body’s immune cells are produced. At this point, cats have a harder time fighting off the virus and may have FeLV for the rest of their lives. The infection can cause anemia (low number of red blood cells) and immunosuppression.

“Having a weakened immune system leaves the cat susceptible to secondary infections, also called opportunistic infections,” says Dr. Rubin. “They are more readily affected by bacteria, viruses, fungi and parasites.” As the disease progresses, it may lead to neurologic disorders, kidney failure, arthritis and abortion in pregnant cats. Because FeLV hijacks the cells’ replicating machinery, it is not surprising that this disease can ultimately lead to tumour growth. In fact, FeLV is the most common cause of cancer in cats, with the most common type of cancer being lymphoma. “A cat infected with FeLV may begin showing signs of lethargy, fever, weight loss, loss of appetite and depression,” Dr. Rubin says.

Since these signs could indicate a variety of diseases, veterinarians diagnose FeLV by collecting blood and performing tests to detect the presence of the virus in the cat. Depending on the clinical signs, the patient may be treated with blood transfusions, medications for opportunistic infections,

immunotherapy, chemotherapy or antiviral medications. “Vaccinations are available,” Dr. Rubin says, “but it is important to remember that they do not provide 100% protection against infection.” Vaccines are important in certain geographic locations where FeLV is more prevalent, such as areas that have a high density of roaming cats. Owners should consult their veterinarian to determine if a vaccine is necessary in their location. Preventive measures should also be taken to reduce the risk.

FeLV can be prevented by keeping cats indoors to avoid contact with outdoor cats. Survival times depend on how the infection progresses and manifests itself, the strength of the cat’s immune system and the type (or strain) of FeLV. Some cats are able to completely overcome the infection while others may suffer from recurrent bouts of infection only when their immune systems are suppressed, such as when they are weakened by another sickness.

Still others suffer from a persisting, also called progressive, form of the virus for the rest of their lives. Cats with progressive infections in multicat households can live up to three years with FeLV. However, survival rates increase when affected cats are kept indoors in single cat households with good veterinary care. To learn more about feline leukemia virus, consult your local veterinarian.

University of Illinois College of VeterinaryMedicine