Part I: What's So Big About the Little Thyroid?

By Jan Cooper

This small gland is a hormone producer that affects many parts of the body. When certain diseases or ailments are suspected in a dog, testing for a thyrod imbalance can often lead to a more accurate diagnosis and better treatment. The little thyroid is more often than not one of the guilty culprits. Edward Baker, VMD, refers to the thyroid as "the body's chief engineer."

This important little gland consists of two oval bodies located in either side of the neck. There are also tiny parts of thyroid tissue in other areas of the chest and even around the heart.

There are two (2) forms of thyroid hormone secreted by the thyroid gland; T3 (triiodothyronine) and T4 (thyroxine). T3 is usable thyroid hormone while T4 must first pass through the liver and other tissues before it can become T3, the usable thyroid.

Here is where it begins to get a little complicated, but I'll do the best I can to help simplify it. The thyroid gland itself is regulated by two different hormones, TRH and TSH. Now, if T4 gets too low, (remember it's not usable yet when it starts traveling around the body) the brain tells the TRH, "Hey, wake up, go get TSH and tell him to get to work!" Now TRH knows that TSH 'hangs out' at the nearby Pituitary gland, and so heads straight there to find him. Well, as soon as TSH hears about the thyroid shortage he races to the thyroid gland and stimulates it to get busy and produce more thyroid hormone. Hence TSH stand for THYROID STIMULATING HORMONE while TRH, being the first one to be released into active duty, is the THYROID RELEASING HORMONE.

As a consequence of all of this, Hypothyroidism (the shortage of usable thyroid in the body) is usually the condition seen when a thyroid imbalance is suspected. Hypothyroidism is becoming all too common in our breed and all of our dogs should be tested.

Why do skin problems seem to go hand in hand with thyroid imbalance? In order for our dogs to have healthy skin and coats, the cells that make up the body must be healthy and multiply. It is not fully understood, but thyroid hormone is essential in regulating the metabolism of each individual cell. Whenever the cells cannot function efficiently, one of the visible results is the skin will loose it's elasticity, and can ultimately result in dry, crusty, scaly skin. The end result can be a dog with a very sparse coat and a dull, almost hardened gray skin that will have a obnoxious odor. A dog left untreated will be miserable with uncontrollable itching all over and will further damage itself by chewing to the point of producing raw and oozing sores, a setting ideal for bacterial infections.

It is found to be a fact that hypothyroidism is definitely associated with reduce resistance and a greater susceptibility to bacterial infections. So if your dog develops any type of skin ailment or a wound that does not seem to respond readily to treatment, you might want to check for a thyroid deficiency.

Part II: Hypothyroidism is Becoming Very Prevalent in the Rottweiler

By Jan Cooper

Last month I explained how the thyroid is regulated by two different hormones, the Stimulating Hormone (TSH) and The Releasing Hormone (TRH). I also explained that because of the amount of thyroid hormone a dog needs, hypothyroidism is the disease usually seen whenever there is a thyroid imbalance or malfunction. This month I will touch on the testing for hypothyroidism and the importance of testing ALL of your potential breeding stock.

There is a lot of confusion about whether a dog has thyroid disease or not. Most people seem to think that they can tell if there is a problem and therefore only then they should take their dog to be tested. When it comes to the thyroid, nothing can be further from the truth.

As thyroid disease develops, it usually starts out as autoimmune thyroiditis. "As what?" you ask. The best way I can explain it is that there are antithyroid antibodies in the blood. In people, this is sometimes referred to as Hashimotošs disease or lymphocytic thyroiditis. The worst part of this is that in 90% of the cases.....it IS genetic! Without testing your breeding stock you wonšt know it until later when clinical symptoms begin to appear. Tragically this may be after the dog/bitch has been bred and then the predisposition for the disease is passed on to the next generation....and so on....and so on.

Letšs get to the testing part, since you should now have a basic understanding of T3 and T4. Remember, T3 (triiodothyronine) is the usable thyroid hormone and T4 (thyroxine) has to be converted into T3? The level of these two hormones is not always inter-related, in other words, the dog may show adequate T4 and yet not be producing enough T3, or visa versa. That is oversimplified, but I think you get the idea.

Most Veterinarians request only the T4 hormone level that is found in the blood to be measured by their lab. But since there is a tiny amount of T4 hormone that is not in the blood, or łfree T4˛, that is also converted and aids intracellular health, this too should be measured. The only way to know if your dog has thyroiditis and later is a candidate for hypothyroidism is to be sure you ask for a measurement of the total T3 and T4 along with a measurement of the łfree T3 and T4˛. Since studies have shown a definite link between the Cholestrol level and T4 in dogs, your veterinarian should also request a cholestrol level from the SAME blood samples. The results of the testing for cholestrol in relationship to T4 is called the łK˛ values.

With the addition of this test, you may detect early thyroid disease before any clinical symptoms are apparent. Once clinical symptoms appear, the łK˛ value can aid in identifying whether the dog has low, normal or high thyroid function.

If there is no local lab that is familiar with these additional tests, then you may wish to talk to your Veterinarian and have him contact:

MICHIGAN STATE UNIVERSITY
ENDOCRINOLOGY SECTION
ANIMAL HEALTH DIAGNOSTIC LABORATORY
P.O. BOX 30076
LANSING, MI. 48909
(517) 353-0621

This article first published in Workingdogs.com and reprinted with permission.

CLINICAL SIGNS OF HYPOTHYROIDISM

By W. Jean Dodds, DVM

ALTERATIONS IN CELLULAR METABOLISM

lethargy
mental dullness
exercise intolerance
neurologic signs (polyneuropathy, seizures)
weight gain
cold intolerance
mood swings
hyperexcitability
stunted growth
chronic infections

HEMATOLOGIC DISORDERS

bleeding
bone marrow failure
low red blood cell count (anemia)
low white blood cell count
low platelaet

OCCULAR DISEASES

corneal lipid deposits
corneal ulceration
uveitis
keraconjunctivitis sicca ("dry eye")
infections of eyelid gland (meibomian gland)

NEUROMUSCULAR PROBLEMS

weakness
stiffness
laryngeal paralysis
facial paralysis
"tragic expression"
knuckling or dragging feet
muscle wasting
megaesophagus
head tilt
drooping eyelids

DERMATOLOGIC DISEASES

dry, scaly skin and dandruff
coarse, dull coat
bilaterally symmetrical hair loss
"rat tail" or "puppy coat"
hyperpigmentation
seborrhea or greasy skin
pyoderma or skin infections
myxedema
chronic offensive skin odor

CARDIAC ABNORMALITIES

slow heart rate (bradycardia)
cardiac arrhythmias
cardiomyopathy

GASTROINTESTINAL DISORDERS

constipation
diarrhea
vomiting

REPRODUCTIVE DISORDERS

infertility or either sex
lack of libido
testicular atrophy
hypospermia
aspermia
prolonged interestrus interval
absence of heat cycles
silent heat
pseudopregnancy
weak, dying or still born pups

OTHER ASSOCIATED DISORDERS

IgA deficiency
loss of smell (dysosmia)
loss of taste
glycosuria
chronic, active hepatitis
adrenal indocrinopathies
pancreatic indocrinopathies
parathyroid indocrinopathies

The above list was graciously provided by W. Jean Dodds, D.V.M. If your dog seems to suffer from any of these ailments, you may want to discuss his/her thyroid with your veterinarian.

Contributed by Alyson Lockwood. It originally appeared in ROTT N CHATTER, October 1992, V.1, N.3, and November 1992, V.1, N.4. May be reproduced without permission. First published in Workingdogs.com.