Hyperthyroidism in Cats


Quick Facts: Hyperthyroidism...

  • Is the most common glandular disorder in cats.
  • Can be found in cats of all breeds and sex.
  • Has an average onset at age 12-13 years (although in rare cases can occur in cats younger than 10).

Clinical Signs Include:

  • Weight loss despite an excellent appetite
  • Excess thirst
  • Restless and needy behavior
  • Intermittent vomiting or diarrhea
  • Urinating outside the litter box

Diagnosing the Disease

During your cat's physical exam, the thyroid glands will be palpated. In normal cats, the lobes of the thyroid gland cannot be felt with your fingers. In a hyperthyroid cat, at least one lobe is usually prominent and may be detected by your veterinarian. A full lab work panel, including a Free T4 by Equilibrium Dialysis, will determine your cat's thyroid function. Findings from the exam and lab work along with noted medical history and clinical signs will help determine a definitive diagnosis. 

Symptoms if Left Untreated

Hyperthyroidism is caused by a benign growth in the thyroid gland that is over-producing T4. Hyperthyroid cats often have a reduced quality of life through weight loss, muscle deterioration, chronic vomiting or diarrhea, heart disease and high blood pressure which can result in heart failure, sudden blindness or sudden death. Good news...all of the above can be prevented with treatment for thyroid disease!

Treatment Options

Radioactive Iodine (I 131)

The gold standard for treatment of hyperthyroidism in cats is a radioactive scan to confirm the disease location and size of the glands followed by a therapeutic dose of Iodine 131. This treatment involves an injection followed by 3-7 days of hospitalization. No anesthesia is required and the treatment is curative. Disadvantages to this option are that the owner is separated from their pet during the hospitalization period and children and pregnant women can have no contact with their cat for 1-2 weeks after therapy. Also during this time, a special flushable litter must be used. This treatment method is not appropriate for cats with kidney or heart failure. I 131 therapy is available locally by referral to the Feline Hyperthyroid Treatment Center of Charleston and is quoted at $975.

Medicating with Methimazole

The most common treatment for hyperthyroidism is a medication called methimazole which blocks the production of T3 and T4. After the treatment has been given for 2-4 weeks, the thyroid levels must be checked and regularly monitored to insure the correct dose is being administered. This option is often popular because the medication is relatively inexpensive and no hospitalization is required. Disadvantages to this method of treatment include the inconvenience and difficulty of medicating every 12 hours. While side effects are uncommon, those that do occur will typically become present within the first three months of treatment. Medicating with methimazole can sometimes unmask or worsen kidney disease. 

Prescription Diet y/d

For the occasional cat who is not a good candidate for routine medication and Radioactive Iodine is financially out of reach, there is a commercial diet available through your veterinarian. Hill's Prescription Diet y/d is reduced in iodine with the idea that excessive thyroid hormone levels can not be produced if there is not enough iodine in the diet to support their production. It is claimed that this diet can normalize a cat's thyroid in 8-12 weeks but must be fed exclusively, meaning no treats, access to other pets' food, or time allowed outside. Once a cat is transitioned to this diet, it is recommended that thyroid levels, kidney parameters, and urine concentration is checked at 4-8 weeks then monitored every 6 months thereafter. 

The Skinny on Urinalysis

Many days in practice, I see clients with the following concern - “My cat is peeing everywhere” or “My dog has to go out 10 times a day!” Either the pet is urinating in the wrong place, urinating more than normal, or the urine looks abnormal.  These are symptoms of problems with the urinary tract, which includes the kidneys, ureters (tiny tubes that drain urine from the kidneys to the bladder), urinary bladder, and/or urethra.

Urinary problems are a big deal. Apart from skin and dental problems, urinary issues are one of the most common concerns of pet owners that come to our practice. Inappropriate urination is also a significant cause of surrender and/or euthanasia in pets. It can be an  incredibly difficult problem for people to manage – causing significant property damage and even worse, frustration with the issue can be very damaging to the human / animal bond.

There are 4 main reasons why pets urinate inappropriately:

  • Anatomic – young animals who inappropriately urinate may have developmental problems of the urinary tract that cause urine leakage (e.g. ectopic ureters)
  • Neurologic – damage to the nerves that control the process of urinating can lead to inappropriate urination for a number of different reasons (e.g. older female dogs with urinary sphincter mechanism incompetence or USME).
  • Disease- infectious, inflammatory, metabolic, endocrine and cancerous diseases can all affect the urinary system and cause inappropriate urination (e.g. bladder stones, diabetes, Cushing’s disease, transitional cell carcinoma, renal disease…)
  • Behavior – some pets may develop inappropriate urination habits secondary to poor early training (sometimes seenin older adopted dogs), territoriality, boredom, fear or even obsessive / compulsive types of problems.

An accurate diagnosis is critical to effective treatment when it comes to urine.  Remember, though tests may be a little costly, treating the wrong thing is ultimately even more expensive.  Imagine treating a behavior problem for several months when actually the problem was an infection that could have been treated with a single round of antibiotics!

For starters, ALL pets that present with inappropriate urination need to have a urinalysis. My vet school clinical pathology professor, Dr. George, used to call it a “liquid renal biopsy”.  There is a lot of information we can get from the urinalysis, which is comprised of three parts:

1) The test strip – this is a color based chemical test that looks for the presence of blood, white blood cells, glucose, protein, ketones, bilirubin (blood breakdown) and checks the pH.  Although not perfectly accurate, they are a good screening test for diseases such as urinary tract infections and diabetes mellitus, to name a couple.

2) The sediment exam – for this the urine is centrifuged, and the cells are examined under a microscope. This is a more sensitive test for the presence of blood, renal casts, fungal organisms and bacteria in the urine, and it also allows us to determine if there are urinary crystals, which can be an indicator of stone formation in the bladder.

3) The urinary specific gravity – This is a number, usually between 1.002 and 1.060, that essentially indicates the density of urine as compared to water. When there is an excess of water in the body, the kidney produces a diluted urine, and the specific gravity will be less than 1.008.  If not, then it produces a concentrated urine, which is indicated by a specific gravity of 1.025 or greater.  The specific gravity will change throughout the day depending on hydration. If the urine is in the middle range, neither concentrated nor dilute, it’s called isosthenuria. If the kidneys are only able to produce isosthenuric urine, it means that the kidneys have lost about 60 – 70% of their functional capability and the pet is in early renal failure. If we can detect renal failure early, before there are changes in the bloodwork, we have a much better chance of managing it successfully for a longer period of time.  If urine is isosthenuric the doctor will often ask you to submit a urine sample from the first morning urine, when it should be more concentrated.

The other test that can be very important in determining the cause of urinary problems is called a urine culture and antibiotic sensitivity. This is where we collect urine in a sterile manner, usually with a needle directly in to the bladder wall (cystocentesis). We then submit it to our reference laboratory, whose technicians apply the urine to a bacterial culture medium. Urine should normally be sterile, so if any bacteria grow, then that is a positive test for a bacterial urinary tract infection.  The lab then tests the bacteria against a number of commonly used antibiotics to determine which ones it is sensitive to so that we know the best antibiotic to use. False negatives can sometimes occur if the pet has been on antibiotics.

Once we have information from the preliminary urine tests, we may move on to secondary testing. For example, if test results indicate the possibility of stones in the bladder, urethra or kidneys, we may do an x-ray or ultrasound to look more closely.  Many other tests exist for following up on urinalysis and culture results that can help us make sure we make the right diagnosis and get the right treatment started for your pet.

I hope this helps give you an idea of how we look at the world of inappropriate urination in dogs and cats. If you have a pet that you suspect of a urinary problem, please bring him or her in for evaluation as soon as possible. If you can bring us some urine that is great, but our veterinary technicians and assistants are pro’s at obtaining urine, so if you can’t, don’t worry, we’ll catch it!

What's that lump?


Dogs and cats are notorious for developing lumps and bumps on their bodies over their lifespans. {Ferrets, guinea pigs, hamsters, rabbits, and rodents are not immune to lump (mass) formations either}. Many of these are benign growths, and often self-resolving, but some may be malignant or infectious in nature so an accurate diagnosis is warranted.

We recommend any new swelling or growth on your pet be examined as soon as possible once detected. We will examine the mass by visual inspection and by palpation. Some common growths may be identified by gross examination alone, for example, oral papillomas and sebaceous adenomas. However, the vast majority of growths need to also have a microscopic evaluation to obtain a diagnosis. This is accomplished by a Fine Needle Aspiration (FNA) of the mass.

Fine needle aspiration is performed in the clinic during most routine exams and sedation is very rarely needed. A small gauge needle is inserted into the growth and gently maneuvered within it. Gentle suction is often applied to a connected syringe. The maneuvering of the needle and the suction help to obtain a sample of the cells that make up the growth. The sample is then delivered onto a slide which is allowed to dry, then stained, and viewed under the microscope. General veterinary practitioners are able to make confirmed diagnoses a vast majority of the time. There are some instances where suspect diagnoses need to be sent to a veterinary pathologist for further identification and/or confirmation.

I try to inform pet owners ahead of time that growths may be "wall-to-wall" cells, so obtaining and observing a cell sample is relatively easy in that case. However, there are many growths where the cells may not exfoliate well or the growth may be more like a blueberry muffin and the abnormal cells are the blueberries that we are attempting to "blindly poke". In these scenarios we may not always get a diagnostic sample (even after repeated sticks with the needle) and so we'll often recommend that a surgical biopsy or complete excisional biopsy should be performed.

It's important to pay attention to any new growth/lump/bump/swelling on your pet and have it examined as soon as you can.  We will often be able to give you a diagnosis of what it is the day we check it out and then lay out a recommended treatment plan.  Many times we'll recommend "watchful neglect", but there are those lumps that may be cancerous or painful to your pet and so the sooner we diagnose the sooner we can manage it.

Is Pet Health Insurance Right for You?

When it comes to insurance, people seem to be in one of two camps: those who love it and those who hate it. For those of you who love it, prefer to pay bills in smaller monthly payments rather than occasional large chunks at a time, or for those that simply have accident/illness prone pets - keep reading!

We recently took some time to really dive into plans from the pet insurance company, VPI, to determine if it could be a worth-while investment for our clients. While there are lots of different pet insurance carriers out there, we chose to evaluate (and ultimately recommend) VPI due to its track record and notable financial underwriter, Nationwide. This said, we're happy to accept any pet insurance plan you choose and encourage our clients to shop around to find the deal that's best for them and their pets.

Before I get into the nitty-gritty of individual plans, let me start by explaining what pet insurance is, and what it is not. In the eyes of the underwriters, pets are treated as possessions and are therefore insured more like cars and less like people. While I personally may not agree with this philosophy, (my dog, Marlie, is practically human!) it does make insurance significantly less complicated. Another aspect to mention is that all pet insurance plans are by reimbursement only. This means you pay for your pet's care at checkout as usual, submit your paperwork, and then the insurance company will send you a check. Plans are available for pets of any age, but have the best coverage and are most affordable if started when your pet is young and at its healthiest.

To help our clients receive the maximum reimbursement possible, one of our receptionists, Lori, is now our official insurance guru. Before submitting your claim, she will scour your pet's medical record and confer with your veterinarian to find the most accurate and beneficial diagnosis to list. With the safety net of insurance, it is our hope that our clients will have the financial freedom to say 'yes' to our veterinarian's best medical recommendations for your furry companions.

Which VPI plan is best for you?

(This is my personal summary of each plan. Please refer to VPI's website: or call 888-899-4VPI for complete information.)

Major Medical Plan

  • Most comprehensive plan with largest reimbursement allowances (typically allows more than enough to have 100% reimbursement for our service prices)
  • Covers injury and illness including chronic conditions, multiple conditions, and advanced diagnostics
  • Covers hereditary issues after 12-month waiting period
  • New plans available for dogs and cats less than 10 years old
  • Plans activate 14 days after application
  • Average premium $15-$40/month based on deductible size, pet age, and pet breed/size.
  • Annual deductible options of $100, $250, or $500 

Medical Plan

(Similar to the Major Medical except...)

  • No hereditary condition coverage
  • Has reimbursement allowancesthat typically will cover 80-90% of our service fees
  • Monthly premium runs a few dollars less

Injury Plan

  • Coverage for accidents only (not medical illness claims)
  • New plans available for cats and dogs of any age
  • Plans activate 24 hours after application
  • Average premium $12/month
  • Flat annual deductible of $250

Cat Plan

  • Coverage for the 15 most commonly seen medical conditions
  • Reimbursement allowance of $600 per condition per year
  • New plans available for cats less than 10 years old
  • Plan activates 14 days after application
  • Average plan $12-15/month
  • No annual deductible

CareGuard Wellness Coverage

(can be added to the above plans)

  • Coverage for wellness exams, vaccines, heartworm prevention, tests, microchips, and +/- spay/neuter/dental procedures
  • Reimbursement allowances will break even for most of our patients
  • Monthly premium $12-22

As with any insurance, there are some products/services/conditions that are not covered in any plan. For VPI, this includes:

  • Food/Nutritional Supplements
  • Congenital/Developmental Conditions
  • Behavior Problems/Training
  • Breeding/Reproductive Conditions
  • Cosmetic Conditions (including declaws)
  • Pre-Existing Conditions

Please let us know if there is anything we can help you with in regards to pet insurance (or anything else for that matter!) If you decide to purchase a plan, please let Lori know and she will be happy to help you with paperwork after each visit.

Canine Hypothyroidism

What is thyroid disease in pet animals?

Your veterinarian may have recently discussed thyroid disease in your dog or cat with you. In dogs, low levels of thyroid hormone, or hypothyroidism, tends to affect middle-aged dogs, and we frequently screen for it on yearly or pre-anesthetic bloodwork. Cats, especially older kitties in their teens, are predisposed to the opposite problem, developing high levels of thyroid hormone, often secondary to a benign hormone secreting thyroid tumor.  Managing these diseases is usually done through oral medication and is often successful in bringing thyroid hormone levels in to their desired normal ranges and controlling the symptoms of the disease. 

Why is thyroid disease important?

Thyroid hormones affect a huge number of systems in the body. During growth and development, thyroid hormones play an essential role in normal formation of the neurologic and skeletal systems. Congenitally hypothyroid puppies often show very stunted growth patterns. Thyroid hormones in adults function in increasing metabolism in the tissues, increasing the heart rate, breaking down fat, stimulating red blood cell production, and regulating cholesterol.   These functions are all affected when thyroid hormones are too low or too high, which results in the symptoms that we see in our patients.

Facts about canine hypothyroidism:

Hypothyroid dogs are usually diagnosed during middle age, on average about 7 years old. About 50% of the time it is caused by a condition called lymphocytic thyroiditis, an immune-mediated condition where the body starts to create antibodies to the thyroid tissue. Other causes can be due to a cancer of the thyroid gland, a secondary condition involving the pituitary, or for unknown reasons, what we call “idiopathic.

Symptoms of hypothyroidism include:

  • Lethargy
  • Strong appetite and obesity not responsive to diet or exercise therapy
  • Fatty deposits in the cornea of the eye
  • Neurologic abnormalities
  • Seizures
  • Vestibular disease
  • Peripheral neuropathy
  • Dermatologic problems
  • Hair loss, especially symmetrical hair loss on both sides
  • Poor re-growth of hair after shaving or clipping
  • Dry and flaky or very oily skin
  • Recurrent skin infections

Diagnosis of canine hypothyroidism

We diagnose canine hypothyroidism through a combination of symptoms, physical examination and blood tests to check for circulating hormone levels.

The thyroid glands are located in the neck just behind the larynx (voice box) in dogs and cats, and actively produce thyroid hormones, including thyroxine (also called T4).  Production of thyroid hormones is regulated by the pituitary gland, through a hormone called thyroid stimulating hormone (TSH).  A feedback loop exists between the body and the pituitary gland, with TSH production by the pituitary going up when the body needs thyroid hormone and turning off when thyroid hormone levels are high.

Screening the blood for indicators of hypothyroidism may include the following tests:

  • Complete blood count – may show a mild anemia in hypothyroid dogs
  • Serum biochemistry – often shows high levels of fasting triglycerides and cholesterol with canine hypothyroidism
  • TT4 – evaluates total T4 concentration in the blood
  • Free T4 (fT4) – evaluates only the portion of circulating T4 that is not bound to protein in the blood.
  • This is a more sensitive indicator of disease. Some dogs that are not truly hypothyroid may have a low TT4 but a normal fT4.
  • TSH levels – may be increased as the pituitary produces more and more TSH to try to stimulate an under-responsive thyroid gland
  • Anti-thyroid antibody – a test that may help determine if autoimmune disease is present

Certain kinds of drugs (e.g. sulfa antibiotics, anti-inflammatory, anti-depressant and anti-seizure medication) can cause artificially lowered thyroid levels so it is important to make sure we account for these before making a diagnosis. In addition, some breeds, such as greyhounds, will normally have lower TT4 levels.

Some non-thyroid diseases can also cause circulating thyroid hormone levels in the blood to decrease. Your veterinarian may need to do other tests to rule these diseases out before confirming a diagnosis of hypothyroidism.

They include:

  • Diabetes mellitus
  • Adrenal disease
  • Hypoadrenocorticism (Addison’s disease)
  • Hyperadrenocorticism (Cushing’s disease)
  • Renal disease
  • Heart failure
  • Severe infections

Treatment of canine hypothyroidism

Treatment for hypothyroidism involves lifelong oral medication with levothyroxine, a relatively inexpensive thyroid hormone supplement. Generally blood tests are rechecked approximately 4-8 weeks after starting medication and again as needed while the dog’s metabolism adjusts to the therapy. After that, once yearly checks are adequate to ensure that the thyroid hormone level remains in the normal range. The prognosis is usually very good for long-term management, but complete resolution of symptoms may take several months.

Next blog from Dr. Rainwater: Feline hyperthyroidism!

Feline Heartworm Disease - What Owners Should Know

Heartworm infection has been a recognized disease in the veterinary world for many, many years but the focus has always been on our canine companions. Spread through the bite of a mosquito, heartworm larvae will continue to mature while migrating to the heart and pulmonary arteries.  In dogs, the juvenile worms mature and develop into adult heartworms. If left untreated, these adult worms will reproduce leading to larger worm burdens within the dog as well as circulating microfilaria ("babies") in the vasculature.  Tests to diagnose heartworms detect either antigen produced by the heartworms, antibodies produced by the dog in response to the heartworms, or a drop of blood, where microfilaria may sometimes be observed.

Cats are an aberrant host for heartworms, so the larvae will migrate to the heart and pulmonary arteries but most often die and do not establish a mature adult infection. The problem for cats arises from the death of these immature worms which sets up a HUGE inflammatory response in the lungs ofan infected animal. Clinical signs may include coughing or dyspnea, vomiting, neurologic signs (from aberrant migration of a larva), or most worrisome - acute collapse and death. The inflammation is often transient, but may last for 6-8 months.  There are some cats (approximately 30% in one study) that may remain asymptomatic and can self-cure.

Due to the atypical infection in cats: very low worm burden, single sex infections, and lack of microfilaria: diagnosis is challenging. The heartworm antigen test lacks sensitivity because of the typical low worm burden and possibility of an all male infection (only the female produces the detected antigen). False negative antigen tests are therefore common; however, false positives are rare, so if positive, an active infection is indicated.  Antibody tests just indicate prior exposure, so these are generally used as screening tests in asymptomatic cats.  In symptomatic cats, combining the antigen and antibody tests give us the best chance of diagnosing heartworm disease. Chest radiographs (x-rays) and echocardiography (ultrasound of the heart) may also be used to aid in diagnosis.

If heartworm disease is diagnosed in dogs, there is an approved drug to kill the adult heartworms (called "adulticide therapy"). Unfortunately, adulticide therapy is not used in cats due to the high risk of death associated with it. Due to this, we often are left with supportive treatment - most commonly with corticosteroids.

Due to difficulty in diagnosing, non-specific treatment, and potential for acute collapse and death as the first (and only) sign of heartworm disease in cats, what is a cat owner living in South Carolina (where the state bird is the mosquito) supposed to do? Prevent the disease from ever occurring is what we recommend! Heartworm preventatives are labeled for use in cats and the two that we recommend are Revolution and Heartgard Plus. 

  • Revolution is a topical flea/heartworm/intestinal parasite preventative, which is often easier to administer to cats. 
  • Heartgard Plus is a flavored heartworm/intestinal parasite chew. 

Both of these products are delivered to the pet monthly, and in the southeast United States, should be done year round.  So, why risk an untreatable and potentially fatal disease for your cat, when you can prevent it completely with regular use of a heartworm preventative?

Find out more on the Know Heartworms website.