Thyroid Disease in Malamutes

Long ago, we had a crabby Malamute.  We were given various "cures" including string her up by the neck until she passes out.  We didn't like that solution so went looking for answers.  We had blood tests done and they all came back normal.  Thyroid was on the low side, but still normal.  So it couldn't be that? Or could it?  In talking to some other breeders at a dog show we discovered it's quite common for Malamutes to have low thyroid.  We were also told, if it's even low normal, supplement. Our vet thought we were crazy, but we insisted on at least trying it.  We had small children at the time and were afraid our dog would snap at the baby.  Lo and behold, it worked.  We got our puppy back (she was 1 1/2) and she was never crabby again...laid back and easygoing, but not crabby.  We were glad we didn't "string her up". 

Hypothyroidism is a common problem in dogs, rampant in Malamutes, and rarely occurs in cats. Virtually every Malamute line has some issues with this complex disease.  It's also one of the easiest and least expensive things to treat.  Thyroid medication is still pretty cheap these days.  A 1000 pill bottle runs about $125 which is about a 6-9 month supply. If your dog requires a dosage between the standard ones, ask the vet if you can get a size that can be broken in half (ie: dog needs .9 so you buy a bottle of .6 and give him 1 1/2 pills) - cheaper than buying a bottle of .3 and .6 since they don't make .9.  Though people thyroid and dog thyroid is the same exact thing (just different brand name) - dogs require a dose 10x the human dose. While human thyroid can be gotten cheaply at Wal-mart under their discounted drug plan, they will likely refuse giving you the Rx for your dog on the premise that it's not a "normal" dose - even though it's the same exact drug and you'd just have to give more pills so ask your vet to order it in quantity for you - that's the least expensive way to buy it. 

The blood test is also fairly inexpensive - about $170 for the comprehensive test sent out to a lab, $100 for the simple test done in the vet's office (Midwest prices 2017).  Don't waste your money on the one your vet does in his 0ffice unless you're pretty sure that's what is going on..  It's not as accurate and can miss something important.  Most of all, if your dog comes back with some low readings, think about supplementing anyway.  It will make a world of difference.  How would YOU feel being tired all the time? In fact recently Jazzy at 9 started...well, actually stopped, picking fights! This was not normal behavior for her to avoid Pod and Simone and let them slide...so we had her thyroid tested. It came back completely in the normal "range". However, by this time we were pretty knowledgeable about our lines and knowing it was 'back there' asked our vet about supplementing anyway. We have a very cool vet in that he agreed....and guess what? We now have our crabby Jazz back...she has the energy now to pick fights and get into the trash like a "normal" malamute. So if it's in your lines (and it probably is) and your dog is not acting quite right - it's probably one of the FIRST things I'd test for. I know of several people whose dogs were not tested at the first sign of something being off, and a couple of years later started seizuring. The vets treated the seizures and never even looked at the thyroid...until the owner mentioned it. When they did, almost ALL of those dogs had thyroid issues. Dr. W. Jean Dobbs has studied this extensively...you may want to read her articles here.

The thyroid gland has a number of different functions, but it is most well known for its role in regulating metabolism by producing thyroid hormones. Hypothyroidism is the condition that occurs when not enough thyroid hormones are produced. Hypothyroidism causes a wide variety of symptoms, but is often suspected in dogs that have trouble with weight gain or obesity and suffer from hair loss and skin problems, though a dog can have a beautiful coat and no problems and still be hypothyroid.  Often you'll find out when something else is suspected.  We had a pup seizure - put on seizure meds - and it was thyroid.  A thyroid test was done and he was low in almost every level.  Hypothyroidism is easy to diagnose with a blood test that checks the level of various thyroid hormones including T3 and T4. Most hypothyroid dogs respond readily to treatment with synthetic thyroid medication such as Soloxine. Many dogs suffer from a low thyroid hormone level for years without treatment. If your dog has chronic recurrent skin problems, or unexplained weight gain, she may be suffering from hypothyroidism.

What causes hypothyroidism?

Hypothyroidism results from the impaired production and secretion of thyroid hormones. The production of thyroid hormones is influenced by the pituitary gland, the hypothalamus, and the thyroid gland. Although dysfunction anywhere in the complicated hypothalamic-pituitary-thyroid pathway can result in hypothyroidism, more than 95% of all cases occur as a result of destruction of the thyroid gland. Most hypothyroidism is thyroid gland destruction that is suspected to be caused by the dog's own immune system killing the cells of the thyroid gland. Hypothyroidism may also be a result of atrophy of the thyroid tissue and resultant infiltration of the tissue by fat, or by a cancer. Hypothyroidism can also be associated with the presence of other diseases and the use of certain medications. Rare cases of congenital hypothyroidism have been diagnosed, as well.

Who gets hypothyroidism?

Golden RetrieverAlthough the onset of clinical signs is variable, hypothyroidism most commonly develops in middle-aged dogs between the ages of 4 to 10 years. The disorder usually affects mid to large size breeds of dogs, and is rare in toy and miniature breeds of dogs. Breeds that appear to be predisposed to developing the condition include the Golden Retriever, Doberman Pinscher, Irish Setter, Miniature Schnauzer, Dachshund, Cocker Spaniel, and Airedale Terrier. German Shepherds and mixed breeds appear to be at a reduced risk of contracting the disease. There does not appear to be a sex predilection but spayed females appear to develop it more often than intact females.

What are the symptoms?

Thyroid hormones are needed for normal cellular metabolic function. A deficiency of thyroid hormones affects the metabolic function of all organs. As a result, the symptoms are usually variable and non-specific. On one hand it may be nothing more than a crabby attitude - on the other the dog can seizure and mimic epilepsy. There is not a specific symptom that is diagnostic for hypothyroidism. There are, however, several symptoms that when combined together make the veterinarian more suspicious of the likelihood of the animal having the disease. A study on hypothyroid dogs revealed the following information on the variety and frequency of symptoms seen with the disease:

This is one of the FIRST things you need to check in a Malamute.  If you are having some non-specific symptoms that don't make sense - check thyroid.  It's inexpensive compared to some things and there is probably a very good chance this is your culprit.  Thyroid deficiency can mimic other diseases - or cause other diseases.  We know of a dog that became diabetic - why? Because low thyroid made him gain way too much weight, and the excess weight caused diabetes.  Had they discovered the thryoid problem earlier, he would have avoided the diabetes and the subsequent vision loss that came with it.    Another started seizuring - when the phenobarbital didn't work they increased the dose (phenobarb can lower thyroid levels even more), and it became a vicious spiral down until he was seizuring so much he died.  Thyroid supplementation might have saved his life.  We'll never know because the vet never tested for it.  Or they could just be crabby or maybe their coat looks dry even though they still seem to have tons of enery...check Thyroid!

Clinical Symptoms Percentage of Dogs Showing Symptoms


Clinical Symptoms

Percentage of Dogs
Showing Symptoms

 
Lethargy/mental dullness
70
Hair loss
65
Weight gain/obesity
60
Dry hair coat/excessive shedding
60
Hyperpigmentation of the skin
25
Cold intolerance
15
Slow heart rate
10
High blood cholesterol
80
Anemia
50 

This has been expanded upon by Dr. W Jean Dodds DVM.  These symptoms are not so common, but have been caused by thyroid disease as well:

Alterations in Cellular Metabolism

  • lethargy
  • mental dullness
  • exercise intolerance 
  • polyneuropathy  <-seen in malamutes
  • seizures <-diagnosed as epilepsy instead?
  • weight gain
  • cold intolerance
  • mood swings
  • hyperexcitability
  • stunted growth chronic infections

Neuromuscular Problems

  • weakness (esp. hind end) stiffness
  • knuckling/dragging feet laryngeal paralysis (bark changes) <- DM?
  • incontinence facial paralysis (droopy)
  • head tilt "tragic" expression (looks old/sad)
  • drooping eyelids
  • muscle wasting (temporal, withers)
  • ruptured cruciate ligament megaesophagus (reflux gastritis)

Dermatological Diseases

  • dry/scaly skin and dandruff coarse, dull coat
  • hyperpigmentation "rat tail" "puppy coat"
  • chronic offensive skin odor, pyoderma or skin infections
  • myxedema
  • bilaterally symmetrical seborrhea with greasy skin
  • hair loss (or dry skin) <- Coat funk???
  • demodetic mange

Reproductive Disorders

  • infertility
  • silent heats
  • hypospermia (low sperm) aspermia (no sperm)
  • pseudopregnancy
  • weak, dying or stillborn pups
  • prolonged interestrus interval
  • lack of libido absence of heat cycles
  • testicular atrophy

Heart Disorders

  • slow heart rate (bradycardia)
  • cardiomyopathy
  • cardiac arrhythmias

Intestinal Disorders

  • constipation
  • diarrhea
  • vomiting

Blood/Bone Disorders

  • bleeding
  • bone marrow failure, which can lead to low white blood cells
  • low red blood cells
  • low platelets

Eye Diseases

  • corneal lipid deposits
  • corneal ulceration
  • uveitis keratoconjunctivitis sicca (dry eye)
  • infections of the eyelid glands
  • Meibomian gland
  • Vogt-Koyanagi-Harada Syndrome

Other diseases

  • IgA deficiency loss of smell (dysosomia)
  • loss of taste

How is hypothyroidism diagnosed?

There are several different tests used to diagnose hypothyroidism in the dog. The test chosen will depend on the symptoms and the availability of different tests to your veterinarian.  In Michigan and nearby states I highly recommend the "test they send to MSU"  which checks all levels of thyroid activity - your vet will know what you mean when you ask for it!

Baseline T4 Test: The most common test run is the baseline T4 test. A blood sample is drawn and tested by radioimmunoassay to determine the level of T4 thyroid hormone in the bloodstream. The T4 hormone is produced only in the thyroid gland and dogs with a failure of the thyroid gland will have a lowered level of this hormone. However, there are other conditions that can cause a lowering of T4 so if this screening test is positive for hypothyroidism another more specific test is often done to confirm the diagnosis.  This is typically the test done as part of a general blood screening.  It can sometimes be done in the vet's office.  It's also not very good at diagnosing thyroid disease as it can miss other important levels. If T4 is low, and even if it isn't, get the more extensive test unless your vet can absolutely rule that something else is going on.

Baseline T3 Test: Another screening test that can be run is the baseline T3 test. T3 is another form of thyroid hormone found in the bloodstream. This test can be used as a screening test instead of T4. The T3 test is not as accurate in early cases of hypothyroidism and occasionally will be normal when the T4 level is reduced. For these reasons, this test is not often used; if it is used, it is in combination with the TSH level or TSH stimulation test.

Free T4 by Equilibrium Dialysis: T4 is present in two forms in the body. The "bound" form is attached to proteins in the blood and is unable to enter the cells. The "free" T4 is not attached to proteins, and can readily enter the cells and perform its function. The free T4 is normally present in very small amounts. A special laboratory test - equilibrium dialysis - has been designed that can quite precisely measure free T4.

TSH Level: This blood test measures the amount of TSH in the bloodstream. In a hypothyroid dog, the level will be elevated because the body is trying to stimulate the thyroid gland to produce more thyroid hormone. If the Baseline T4 and Baseline T3 are low and the TSH is elevated, a diagnosis of hypothyroidism can be made.

TSH Stimulation Test: If a dog has a low T4 or T3 level, this test may be performed to confirm a diagnosis of hypothyroidism. A small amount of Thyroid Stimulating Hormone (TSH) is injected into the vein. After 6 hours, a blood sample is drawn and the T4 level is checked. A dog without thyroid disease that may have other conditions causing a low T4 will have a high T4 level after the TSH injection. A dog with true hypothyroidism will not have an increase in T4 after the injection.

As mentioned earlier, 95% of thyroid disease is caused by destruction or loss of the thyroid gland function. If hypothyroidism is suspected but not confirmed by these three described tests, then it is possible that the condition may be caused by one of the other 5% of conditions that cause hypothyroidism. To diagnose those problems, one or several of the following tests may be used: TSH stimulation test, serum total reverse T3 concentration (a radioimmunoassay), serum free T4, and serum free T3 concentration.

How is hypothyroidism treated?

A hypothyroid dog will need to be on thyroxine for the rest of his life.  It's a small pill you can hide in his food - usually given once or twice a day. You can't give a dog human thryoid medicine because they require a dose 10x stronger to be effective.

Hypothyroidism in dogs is easily and inexpensively treated. Treatment consists of placing the dog on a daily dose of a synthetic thyroid hormone called thyroxine (levothyroxine), brand name Soloxine. The dose and frequency of administration of this drug varies depending on the severity of the disease and the individual response to the drug. A dog is usually placed on a standard dose for his weight and then blood samples are drawn periodically to check his response and then the dose is adjusted accordingly. Once therapy is started, the dog will need to be on treatment for the rest of his life. Usually after the treatment is started, most of the symptoms resolve. 

Thyroid Disease in dogs and the connection to SEIZURES - (it may not be Epilepsy after all)