CANINE AUTO-IMMUNE THYROID DISEASE

Sylvia Evans

Information and case histories

Vets continue to recognise and acknowledge that within the last decade there has been a significant increase in the occurrence of the Auto-Immune and Allergic disease(s) in our canine population Whilst some of this can be attributed to environmental influences effecting genetically susceptible individuals, the inbreeding and the line-breeding, commonly practiced in purebred stock over generations, is said to place them at a higher degree of risk.
Of more than 40 disorders of auto-immune nature, susceptibility to almost ALL is influenced by genetic makeup. "Trigger Factors" can influence the outcome of progression in those dogs who carry the genetic makeup; however not all littermates will necessarily be affected.

A number of Auto-Immune conditions are now well documented in the Afghan Hound including some of the bleeding disorders, (see article in the 2002 edition magazine) but of these AI conditions, Canine Autoimmune Thyroid Disease (thyroiditis) is possibly the most commonly acknowledged, indeed in the recent Breed Council Health questionaire, although poorly supported and probably not giving a balanced view, did highlight a significant number on reported Hypo-Thyroid disease.

Thyroid disease is not uncommon in Humans, Cats & our Dogs. DOGs get Hypo-thyroidism (underactive thyroid) CATs get Hyperthyroidism (overactive thyroid) and HUMANs commonly get BOTH!
The thyroid gland produces hormones essential to well being. They have an important role in the regulation of all body cells, and are essential in controlling metabolism.They assist in regulation of body temperature and are an essential part of the immune system in fighting infection.They help brain function and maintain alertness, awareness and energy. In short the thyroid hormones are ESSENTIAL to a healthy lifestyle .
Hypothyroidism in the dog is when the gland slowly atrophies, the ability of the thyroid to produce these essential hormones in controlling metabolism progressively diminishes and the body will start to run out of these hormones known as T4 and T3.When there are not sufficient hormones being produced, clinical signs will appear.
Most of the confusion about diagnosis and the treatment of this condition stems from expectations that an affected dog must show clinical signs of inadequate thyroid hormonal production in order to have the disease.
Using the words of Jean Dodds, the acknowledged veterinarian world authority on Canine Thyroid Disease....."The term HYPO-THYROIDISM has been loosely applied to describe ALL stages of this complex disease process when strictly speaking the term should be reserved for the END stages of the illness, when the animal's gland is no longer capable of producing sufficient hormone(s) to sustain health."
It is at this final stage that a dog can express any one or a multitude of symptoms that can affect the whole of the body's system.
This process can take years, from the commencement of the condition before significant signs may appear, by this time around 75o/o of the thyroid may have then been destroyed. Owners may have been aware of some significant changes in their dog's health patterns.

This is an immune-mediated disease that can develop in ANY genetically susceptible dog and it is characterised by the presence of anti-thyroid antibodies in the blood or tissues. It is believed to commence around the age of puberty and gradually proceed until signs start appearing, commonly in the middle/5 years upward, to the older age range groups, BUT some dogs are now showing significant signs much earlier (from 2 years of age or even younger) During this process the animal may also become more susceptible to a variety of immune-mediated or other health disorders affecting vital organs.
This is a proven genetic disorder with a strong familial pattern.
Hypo-thyroid disease is NOT just about a fat lethargic middle aged dog as so many people seem to believe. It can be a very difficult illness, left undiagnosed, for both dog & its owner in caring . The depletion of the thyroid hormone can result in obvious signs and some NOT so obvious of the "root core" underlying deficiency.
Dogs with Hypo-T are MORE prone to develop OTHER Auto-Immune disease(s) especially the Endocrine diseases, for example acute pancreatitis; Other conditions include heart disorders such as cardiac arrhythmias, cardio- myopathy. and especially behavioural patterns with changes in temperament. In studies in America, results have indicated a significant existence in thyroid disfunction and aggression as well as seizure related disorders.......but it is a disease that IF diagnosed correctly, can be successfully treated, including a control in some of these "Other" symptoms. There may be a few minor set backs and it is always advisable to maintain regular monitoring of the thyroid levels by frequent blood testing to control levels of medication*
Diagnosing the condition might present with some degree of difficulty. There are a variety of blood tests available but none may be totally conclusive.
This may help understand why there is much controversy within the veterinary profession, certainly here within the UK, whether or not testing or treatment is indicated for those dogs that clinically may fail to show the text book physical signs of Hypo-Thyroidism.

From my own experience with my own dogs who have/had the condition diagnosed, and other later associated immune- mediated disorders, it is myself who have requested, from my own vets, the specific testing, including a FULL Thyroid profile.

The most useful tests available are.
Total T4: this is the most important thyroid hormone and too often it is the ONLY test some vets will perform but it is much more preferable to have a FULL THYROID PANEL PROFILE undertaken because taken on its own it is NOT sufficient to determine true hypo-thyroid disease. In times of stress, systemic illness, oestrus cycles, drugs etc, base levels of T4 can be much lower. Cushings Syndrome: Diabetes, Liver & Kidney Infections can also show low levels ,this dog may not have a thyroid problem.

Free T4. (in the past different methods have resulted in a complicated measuring of the levels but this is a very useful test and can be especially useful in differentiating between a genuinely hypo-T dog and one showing signs as a result of an illness that may affect production of the thyroid hormone, these are known as "Sick Euthyroid Dogs):

TSH (Thyroid stimulating hormone) This is produced in the brain by the Pituritary gland and stimulates the Thyroid gland to produce its hormones, it is a useful test. A HIGH TSH result may indicate Hypo-T disease even IF the T4 may read within normal reference range and be an indicator of problems surfacing later.
You can get T4AA and T3 AA (auto antibodies against T3 and T3 hormones) tests from thyroid profiles performed on samples sent to the USA.
TgAb, thyroglobulin auto-antibodies test, can be undertaken here in the UK. (PAW) This test does NOT tell you anything about the actual Thyroid gland but it is a useful "Marker" as its presence indicates the disease process & future development.
Vaccines can produce auto-antibodies against the thyroid.
To date Hypo-Thyroiditis is the only endocrine disease that has a test for auto-antibodies....but we do not know if VACCINES produce auto-antibodies to any other parts of the body that may be a "TRIGGER" for OTHER Auto Immune conditions to develop.
I am NOT going into the arguments for or against VACCINATION in this article, this must be a personal choice for each owner and with whatever the owners feels most comfortable .......BUT.... I would question the practice of the frequency in BOOSTER VACCINATION's to our dogs.
With all the millions of dogs who do have vaccines, the majority will not develop Auto-Immune Thyroid Disease. Possibly all have nasty antibodies floating around the system but are there are only problems with an inherited compromised immune system? This is something to be considered and may serve to explain why so many families may be affected....so we are back to the GENETIC makeup once again.

Diagnosis Hypo-Thyroid disease can be a complicated process but is without doubt now becoming more clear to the professionals (the USA vets have been way ahead of us here in the UK for some years and this is why I personally have always chosen to have many of my tests sent to the USA for a broader in depth picture has have many other owners in a variety of breeds ) but more and more tests are becoming reliable here on "Home Territory" now, especially GLASGOW Vet School and the work of Richard Dixon. Many of the tests that were once considered to be reliable in past years have now been removed and there is much practical help out there from those veterinary "Experts" specialising in Endocrinology for your own general in-practice Vets to seek out if there are doubts with diagnosis.
Eventually it is hoped that a genetic marker will be found for Auto-Immune Thyroiditis, this will eliminate the problem of breeding apparently clear dogs that may later go on to develop the disease but that is a long way off as yet, even the PAW Screening test (to identify the dogs that may be carrying the TgAb factor and who will become Hypo-Thyroid eventually is only of value for that one limited CLEAR sample, there is NO gurantee that the TgAb factor will not show in any subsequent samples so it is recommended that this is a test that is repeated on a bi-annual basis , but it is a start.

Any thyroid screening is less likely to serve any useful purpose before puberty. Screening between 12/14 months males, and during the first anestrus period for females following their first season, approx 12 weeks from the onset of the previous heat. (Season cycles can have an effect on the results in females hence this suggested time period for the testing.)
Healthy young dogs (less than 15-18 months) should have Thyroid baseline levels for all parameters in the upper half to one third of the adult range, remember that ALL SIGHT HOUNDS do have LOWER base levels as NORMAL and this must be taken into consideration by the laboratory services.
The treatment for the diseases is the replacement of the hormone in tablet form (trade name SOLOXIN). The dosage of supplement for a Hypo-Thyroid Sight hound is typically about one half of the twice daily dosage given to other breeds. ie 0.1mgm per 20lb body weight twice daily)
Most dogs do extremely well on such medication. Life expectancy is near normal and the quality enhanced, certainly adequate, although there may well be significant subtle differences observed by the owner. Some dogs may show only partial or poor response to such medication due to either poor absorption of the drug or poor conversion (some dogs with liver dysfunction) and these dogs may require specific combination thyroid hormone drug replacement to "kick start" the process.
A dog may also go on to develop & exhibit certain "problems" that will be related to the immune system.
My own dog NUREYEV was diagnosed with Hypo-thyroid disease in 1999 and remained very well and controlled on Soloxine, with regular blood testing we were able to monitor his function and review his medication as necessary, generally it was an upward curve. We did have to make increasing adjustments in the final year of his life. Unfortunately he went on to develop the POLYGLANDULAR AUTO-IMMUNE SYNDROME in the final months of his life & despite the very best in veterinary advice from specialists both at home & in the USA, when it became too obvious that his quality was fading it was kinder to say goodbye, he was by then almost 11yrs. His litter sister, ANGELINA BALLERINA is now turned 12 years, she has been on supplement since 2000 & is like a 2 year old, witness her "Performance" when she came along to the 2002 CH show to collect her Veteran Of the Year Trophy ! , she is maintained on a very basic level of dosage.

Follow up testing after initiating treatment is generally carried out 6/8 weeks after commencing therapy with the blood samples being taken 4/6 hours after the morning dose. Dogs on regular medication should have a complete thyroid panel (not just T4 as you need to be sure that the dog is converting the T4 medication properly to T3) on a regular 6/12 month basis.

I have only attempted to cover the very BASICS of this complicated disorder but I hope it will help highlight a very significant condition that we are now recognising as being far more common within our breed and hope it is a subject that will assist ALL owners/breeders for the future. If I can be of any help at anytime with my own experiences please feel free to contact me.
If individuals are prepared to raise health issues, stand together & discuss such, this is the way forward. I appreciate that it is NOT always that simple! I know I have "Ruffled a few Feathers" when I have attempted to raise some very basic questions. It is obvious to me now that I have a better understanding of this complex condition that in all probability the dam of both NUREYEV  and BALLERINA, my MADAM GAYE was showing signs of Thyroiditis, certainly in her middle years and this may well account for why she was so ill post-whelping her litter in 1991. Previous generations of some of my dogs (same family lines ) have gone on to develop Laryngeal Paralysis .We are now aware that this neurological condition of LP, a common condition in the elderly Afghan Hound, can also be associated with Hypo-T, as is Muscle Wasting and SOME Seizure related disorders frequently simplistically diagnosed as Epilepsy
..DNA testing, long term, will be the obvious way forward but it is NOT going to happen overnight! and certainly for Hypo-T will require a lot of breeder co-operation involving families of dogs, The reason family information and DNA is so vital, is to show how the DNA amongst family members is similar, or not and also each breed may have to be studied individually. Different breeds may or may not have identical genetic makeup, we have already seen the "Difference" with the Sight Hound Breeds in basic thyroid levels of normal!. In the interim therefore I am firmly of the opinion that education of ALL of us as the CUSTODIANS of our BREED(S) in relation to HEALTH matters is the BASIS for EVERYTHING. Breeders must not only be AWARE but SENSITIVE to health related problems that may arise in their breeding stock. If some breeders choose to be secretive about the health problems encountered within their breeding lines, well that is their choice... BUT.... it serves NO useful purpose long term to attempt to keep such information "In House". The attitude of the Breeder toward HEALTH is paramount to the FUTURE of any breed

With grateful thanks & reference to lectures/ papers on the subject that I have attended given by JEAN DODDS: DVM.USA.
RICHARD DIXON: MRCVS. PHD UK.

POLYGLANDULAR AUTO-IMMUNITY
Individuals genetically susceptible to auto-immune thyroid disease may also become more susceptible to immune-mediated diseases affecting other target tissues and organs, especially the bone marrow, liver, adrenal gland, pancreas, skin, kidney, joints, bowel and central nervous system. The resulting polyglandular auto-immune syndrome of Humans is becoming more commonly recognised in the Dog and probably occurs in Other species as well. This syndrome tends to run in families and is believed to have an Inherited basis.
Multiple endocrine glands and non-endocrine systems become involved in a systemic immune mediated process....In short the body system starts to destroy itself. The auto-antibodies are destroying all vital functions.
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GRAN MAL FITS & HYPO-T  A personal experience
The owner of OLIVER, has kindly allowed me to include the following from her own experience.
"It is amazing how many vets here (UK), don't pick up Hypothyroidism as they frequently only do the T4 and possibly TSH testing . It is only by us asking and our vets agreeing to more in depth testing and positive results that vets here in the UK will begin to accept its existence.  I will not bore you with his full story but Oliver was severely Hypothyroid. Because the T4 and TSH tests performed here, plus ECGs, scans countless blood tests etc showed nothing really wrong.....BUT... within 9 months he started having Grand Mal Fits, he was that bad! I sent his bloods to the USA, results back in a few days. He was immediately put on to Thyroid supplement and his seizures stopped.....Just like that!....His coat and persona improved beyond recognition, to the point that I still barely forgive myself for my ignorance in not noticing the difference over the preceding months. Re-testing, according to Dr Jean Dodds advice, keeps on top of it and thyroid medication really DOES work!
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An excellent web site for further information concerning HYPO-T and EPILEPSY is
www.canine-epilepsy-guardian-angels.com

SYLVIA EVANS (AMSHURA) September 2003.

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