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Two Health Articles from Sweden:

 

 

A Swedish health project focusing on diabetes mellitus
and hypothyroidism

 written by  Tove Dahl, DVM, PhD student, Faculty of Veterinary Medicine,Swedish University of Agricultural Sciences

 

and

 

Thyroid problems in PONs;
autoimmune thyroiditis

Written by Eva Johnsson, DVM, for the Swedish PON-magazine.

 

 

 

A Swedish health project focusing on diabetes mellitus
and hypothyroidism



Written by Tove Dahl, DVM, PhD student, Faculty of Veterinary Medicine,
Swedish University of Agricultural Sciences, tove.dahl@kirmed.slu.se


Several cases of diabetes mellitus and hypothyroidism have been reported from Polski
Owczarek Nizinny (PON) owners in Sweden. If not correctly treated, these diseases
severely affect the dog. Both diseases demand a life-long treatment. In order to investigate if there is a genetic background for these diseases in the PON breed, a group of researchers from the Swedish University of Agricultural Sciences will co-operate with
the Swedish PON union. Health information and blood samples will be gathered from as
many PON dogs as possible and the results are intended to be published internationally.


Diabetes Mellitus

This disease is common among humans, dogs and
cats. It develops when an animal has a deficiency of
the hormone insulin or when something blocks the
effect of this hormone. Insulin is essential for the
cells in the body to get sugar from the blood. When
an animal has diabetes mellitus, it has too much
sugar in the blood and not enough sugar in the cells
where it is needed as the prime energy source. The
high sugar level in the blood makes the animal very
thirsty and tired. The diabetic state is dangerous for
the animal and must be treated with daily injections
of insulin. The dog is normally treated initially at
a veterinary clinic and then at home by the owner.
As in people with diabetes, some other life-style
changes such as change of diet often need to be performed. A diabetic dog can live a good-quality life for several years. The causes of diabetes in dogs are
still unclear and probably vary among the different breeds.

Hypothyroidism


This disease is due to a deficiency of the hormone
thyroxin. Thyroxin normally regulates the animal’s
metabolism. If a dog has a lack of thyroxin, many
things in the body run more slowly. Often the dog
gets fat although it eats less. Other symptoms may
be tiredness, slow heart-rate, hair-loss and skin infections. The therapy is daily oral supplementation with thyroxin. An interesting aspect is that a diabetic
child often gets hypothyroidism when it gets older. In dogs we don’t know yet if there is such a connection.

Research Project

The project will be a part of the new Swedish research project ”Canine diabetes mellitus” in Sweden.

1. Health investigation


We will collect information about the health situation in the 400 registered dogs in Sweden. This will be done via questionnaires and interviews with breeders and owners. When a case of diabetes or hypothyroidism is found, it will be confirmed either by blood samples or veterinary records. These data will be used to analyse how the disease genes are transferred from one generation to another. All information will be handled confidentially.


2. Blood- and urine samples


In the first stage we will focus on dogs with diabetes. We will collect blood and urine
samples from as many diabetic PONs as possible. In order to achieve this we have an
agreement with veterinary clinics nationally to help us. The project has a homepage in
Swedish (http://clinic-smallanimals.slu.se/hunddiabetes), where owners and veterinarians can find information about the disease and the project. The blood samples will be
used for DNA-testing and also for finding markers of autoimmune disease. In the
second stage, studies of hypothyroidism is planned in order to search genetic markers.


3. Family study


Owners of both healthy and diabetic dogs in a few families will be contacted for further
investigations. Some of them will be asked to perform a glucose tolerance test which can
indicate if the dog is prone to develop diabetes.



International cooperation?


It would not be surprising if PONs in other countries
suffer from the same disease panorama. If you and your breed union are working with the same diseases and want to share your experiences, or if you as a
PON-owner, breeder or veterinarian are interested in the project, don’t hesitate to contact the writer of this article.


Results

We hope that these investigations will increase the knowledge about the diseases and also identify risk factors within the breed. This could improve the possibilities of an early correct diagnosis and appropriate treatment. If we find a genetic marker it could be
an important step for making the PON breed healthier. Potentially, such a genetic marker could also be of great importance in the research about human diabetes and hypothyroidism.



Thyroid problems in PONs;
autoimmune thyroiditis



Written by Eva Johnsson, DVM, for the Swedish PON-magazine



Introduction

This article is a simplified description of the thyroid problems occasionally occurring in the PON, how the diagnosis is made, a short description of the illness and why you ought to test your dog. It is not intended to cover the whole area in this rather complicated subject, for a more in depth knowledge one should read the
huge amount of published data covering this subject.

Background

Hypofunction of the thyroids is a common problem in several breeds. Primary hypofunction of the thyroids (that is the thyroid itself is affected)
is the most common. This disease is usually classified as lymphohistocytic thyroiditis (autoimmune) or idiopathic thyroiditis.

Autoimmune thyrioditis is caused by a production of autoantibodies by the dog, which in
the end results in a hypoplasia of the thyroids. In the case of idiopathic thyroiditis the cause for the hypofunction is unknown/undetermined.

A hypofunction of the thyroids could also be secondary, i.e. caused by external factors such as low production of the hormone that stimulates the thyroids (TSH), some medication or after infections.

Autoimmune thyroiditis has a genetic disposition in several breeds, including PON.

How does the thyroids function?

The thyroids are a paired glandula situated on both sides of the trachea. It produces with the help of iodine two hormones (T4) and triiodo thyronine (T3). These hormones circulate in the blood and affect the energy production in all the
cells in the body and also the growth. The production of these hormones is controlled from parts of the brain with the help of other hormones, thyroid releasing hormone
(TRH) that is secreted from the brain (hypothalamus) and stimulates the production of thyroid stimulating hormone (TSH) from the pituitary
gland, which in term stimulates the secretion of T3 and T4 from the thyroids.

Simplified this function could be described as a thermostat. When the amount of free circulating T3 and T4 has dropped below a certain level in the blood a signal is sent to the brain.This signal starts the production of TRH in the
hypothalamus, which in term signals to an increased production of TSH, which stimulates
the production of T3 and T4 in the thyroids.When the amount of T3 and T4 increases in
the blood to the desired level a signal is sent to the brain to reduce the secretion of TRH and subsequently TSH. This mechanism is therefore
called a feed-back mechanism.When the thyroids itself cannot produce the
desired amounts of T3/T4 (primary hypofunction), the amount of TSH is increased trying to stimulate the thyroids to increase their production of T3/T4.
T3 and T4 circulate in the blood bound to protein with a small amount circulating unbound(so called free fraction). It is the free fractionthat is active and can pass through the cellmembranes. The protein bound part work as the reservoir.


What are the clinical signs of
a hypothyroid dog?


The thyroid hormones affect almost the whole body and therefore the clinical signs might vary. Usually a change in the coat (alopecia, dry coat,slow hair growth) is seen. Other symptoms are tiredness, obesity, skin problems, ear problems,changed behaviour and a change in the heart rate.

Diagnosis

The diagnosis is made based on the clinical signs and a battery of blood tests.
When hypofunction of the thyroid is suspected, total T4 and free T4 and sometimes cholesterol are usually measured. This panel is used to determine if the dog is hypothyroid or not at the time the measure is performed and will not
predict the future. A point to observe is that the amount of total T4 could be below the reference rage even if the dog does not suffer from any thyroid problems. A low value of protein bound (total) T4 but normal TSH and free T4 does not suggest
a hypofunction of the thyroids and the cause should be looked for elsewhere. Problems that cause low total T4 could for example be chronic inflammation, liver problems, treatment with cortisone and several other medicines. In man, an increase in TSH is a certain diagnosis of hypothyroidism, but that is not the
case in the dog. In dogs it is recommended to analyse at least TSH and free T4. However, it is utmost important to make a full investigation
background of the dog and clinical signs before making a definite diagnosis.

.

Autoimmune thyroiditis

In several breeds, including PON, exist an ill ness caused by a primary hypofunction of the thyroid. The dogs own immune system attacks and destroys the thyroids, so called autoimmune thyroiditis. Since this illness shows a
genetic disposition (inherited) it is important to try to limit/reduce the prevalence in the breed. Dogs affected by autoimmune thyroiditis have
circulating autoantibodies against thyroglobuline in the blood. These circulating autoantibodies can be measured with a simple blood test
(thyroglobulin autoantibody test, TgAA test).
This test does not tell if the dog is hypothyroidit or not – it tells that the dog is producing autoantibodies. It can take several years before a positive dog will develop autoimmune thyroiditis, although most dogs will need treatment within a couple of years. That is, a dog positive for TgAA can be clinically healthy, but is – despite this fact – a carrier of the disease and will eventually develop hypofunction of the thyroids. False positive results can be produced if the dog has high amounts of other circulating antibodies. It is therefore not recommended to perform the test when the dog has had an infection, or within two months after inoculation. False negative results could be seen with an incorrect performed analysis, if the dog is treated for hypofunction or in the case when the whole thyroid is destroyed. In the latter case the dog
should show serious clinical signs. The TgAA test is a ”marker test” for autoimmune thyroiditis and will not predict the actualfunction of the thyroids. For the function of the
thyroid the whole battery of tests is required. Autoantibodies are usually developed between the ages of 2-6 years. It is also important that
the test is performed at a licensed laboratory.

Why should I test my pet dog?

Autoimmune thyroiditis is an illness with a genetic disposition. At the moment the mode of inheritance is unknown in the PON. In humans a similar illness is known, Hashimotos disease, which is believed to have a polygenetic trait. In order to reduce the incidence of autoimmune thyroiditis in the breed, it is important to know in
which combination of dogs the illness occur. To be able to know that, it is important to know the test results from as many individuals in as many litters as possible. Naturally also the positive test results is required and not only
the negative!

Today the only way to advice breeders on how to avoid thyroiditis in their breeding program and also to establish how the illness is inherited and possibly also develop a DNA-assay in the future is to test as many dogs as possible
and submit the results.

To test also pet dogs that are not intended for
breeding will contribute to a healthy breed. The
test should preferably be performed at the earliest age of 2 years and also after 6 years of age. After 6 years of age it should also preferably be
combined with a full thyroid test panel.

Testing for autoimmune thyroiditis can be compared with x-raying for HD (hip dysplasia)
as an example. When evaluating HD it is quite natural to include the whole litter and that ought to be the same for autoimmune thyroiditis.

What do I do if my dog tests positive for TgAA?

If the result comes back as positive one should consider doing the whole blood screen
to measure the function of the thyroid. It can take several years before the dog develops
hypofunction of the thyroid requiring treatment. The treatment consists of giving the dog
supplementation of thyroid hormones (levaxin): The treatment is life-long, but the dog can enjoy a completely normal life.

Do you have questions about breed-related health problems (for example hypothyroidism or diabetes)? E-mail the Swedish PON-club:

  avelsrad-merja@ponunionen.se

and we will try to answer your questions