Project Hope and Hypothyroidism

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Hope after successful treatment for hypothyroidism

Project Hope

Hope, the first dog taken into NGWPR foster care, remained in long term foster care with a loving family until her death. When first evaluated, she was hairless, lethargic, and near death with undiagnosed and untreated thyroid disease. She was also was extremely fearful. With loving, patience, and good medical care, she lived a wonderful life, and while in some situations still shy, the fear dissipated with treatment. Hope’s remarkable transformation served to educate many about this devastating disease.

As many rescue dogs may suffer from this illness, the National German Wirehaired Pointer Rescue organization believes that we are responsible to screen dogs at high risk before offering them for adoption.

Due to generous donations from Chuck Casanova and Robin K Nelson, DVM and Brian and Leslie R Dye, MD to begin funding for this project, these foundational contributions and additional donations will allow us to test all male rescues, aged 2–4 years and any dogs with symptoms (the groups at highest risk) with antibody testing. The cost of testing can be up to $200 with shipping, as only specialized laboratories offer the testing.

To donate to Project Hope, just go to the donation form (Click here to donate to NGWPR) and indicate that your donation is for “Project Hope.”

Canine Hypothyroidism: Anything New?

This article is reproduced from the Fall 2020 issue of Wire News with permission from Wire News and the author, Robin Nelson, DVM. Please find take home points at the end of the article.

Background

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What is the thyroid gland and what does it do?

What causes hypothyroidism in dogs?

Signs and Symptoms of Hypothyroidism

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Hope before treatment

Hypothyroidism can affect the heart causing bradycardia (slow rate) or an abnormal rhythm. Other conditions suspected of being associated with hypothyroidism include megaesophagus (digestive tract problem causing regurgitation) and laryngeal paralysis (difficulty breathing). In moderate to severe cases of hypothyroidism, obvious thickening of the skin occurs secondary to accumulation of glycosaminoglycansan resulting in an obviously puffy appearance and thickened skin folds above the eyes. This puffiness, together with slight drooping of the upper eyelid, gives some hypothyroid dogs a very distinct “tragic” facial expression. A rare syndrome in the extreme expression of hypothyroidism is myxedema coma.

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A rare syndrome int eh extreme expression of hypothyroidism is myxedema coma

Hypothyroidism is suspected of causing aggression or abnormal behavior in German Wirehaired Pointers. In one retrospective study performed at MSU, there was actually a negative correlation between a history of aggression and hypothyroidism translating to…dogs with a history of aggression were LESS likely to be hypothyroid. Michigan State University states there have been anecdotal reports of canine hypothyroidism resulting in aggression which may be the effects of hypothyroidism making a dog “irritable.”

Some dogs show few, if any, signs of hypothyroidism other than behavioral problems

What happens to people with hypothyroidism?

More signs and symptoms

Possible seizures, manifested as dangerous episodes of aggression, have been speculated about for decades. Terms used over the years to describe dangerous aggression include: limbic seizures, psychomotor seizures, rage syndrome, episodic dyscontrol, mental lapse aggression, and sudden onset idiopathic aggression.( SOIA) Sadly, the link between seizure activity and aggressive behavior in dogs also remains poorly investigated. There is very little information in the literature. These dogs may or may not have underlying thyroid disease. Episodic dyscontrol or rage syndrome was diagnosed using clinical history, electroencephalographic findings, and response to treatment with phenobarbital in a few dogs. Clinical features included a mood change, possible irritability heralding aggressive outbursts directed at people or objects, and a post- aggression phase characterized by lethargy and lack of responsiveness. At some point, the mood changes are so extreme and the behavior so different that another explanation is sought to replace the original more typical “dominance-related aggression” label. Owners become able to detect these mood changes in their dogs prior to aggressive outbursts of growling, barking, and biting. Aggression is more likely to occur when the dog is tired and can sometimes be triggered by loud noises. Eyes become glazed, pupils dilated, and the dog enters a “trance-like” state.

Episodic dyscontrol is described as outbursts of aggressive behavior in children and adults with boys being affected more frequently than girls. By definition, episodic dyscontrol in humans consists of recurrent attacks of uncontrollable rage usually with minimal provocation and often out of character. There is sometimes a family history of violent behavior especially in the case of fathers, suggesting a genetic component. More research is needed to determine if these episodes are due to transient hormonal factors, learned behaviors or some type of aggression threshold breakdown. The most important diagnostic pointer for episodic dyscontrol is the lack of provocation to justify this type of behavior.

The most important diagnostic pointer for episodic dyscontrol is the lack of provocation to justify this type of behavior.

A German Wirehaired Pointer being considered for a breeding program needs to be tested for thyroid disease.

OFA Rank and Thyroid

The GWPCA has lowered its OFA thyroid profile rank and increased normal thyroid profile numbers by not breeding dogs with immune-mediated thyroiditis.

GWPs ranked 9th in breed statistics for thyroid disease through December 2012 with a total of 385 GWPs tested: 11% were abnormal, 76% normal with the remaining 13% equivocal. Our CHIC Program required an OFA Thyroid profile beginning in 2008. There have been a total of 1033 OFA thyroid evaluations for GWPs from 1974–2019. Increased numbers of OFA thyroid profiles prove our members recognize and test for thyroid disease in our breed. A total of 648 OFA Thyroid profiles have been run in 7 years allowing our GWP rank to drop from 9th to 16th. 80.3% of dogs tested Normal, autoimmune thyroiditis affected 8.5% of GWPs and 10.7% tested Equivocal.

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Whether testing a GWP in a breeding program for immunemediated thyroid disease or screening a dog based on clinical signs of the disease, ALL thyroid profile numbers must be examined in conjunction with clinical evaluation of the animal. An annual chemistry profile which includes a TT4 is an excellent “screening tool” for hypothyroidism if a dog is clinically normal and not being used in a breeding program. Many commercial labs include a TT4 in a metabolic panel for a nominal fee. If the TT4 is low and the panel shows elevated cholesterol levels or a mild non-regenerative anemia, more testing needs to be done. Approximately 75- 80% of hypothyroid dogs have elevated fasting cholesterol levels. A mild non-regenerative anemia is present in 30–40% of hypothyroid dogs and should be pursued with further testing. SDMA, a newer biomarker for kidney disease can also be significantly higher in hypothyroid dogs.

GERMAN WIREHAIRED POINTERS showing clinical signs suggesting thyroid disease or unexplained behavior or aggression should be tested for hypothyroidism

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Testing for Hypothyroidism

State-of-the-art assay technology is constantly being refined to determine a correct OFA thyroid classification. Currently, OFA Thyroid Profiles include:

The vast majority of dogs with hypothyroidism have a serum T4 below normal, but some NORMAL dogs may have a low T4. In-house testing of TT4 is NOT recommended since 50% of normal dogs have a low serum T4 at some time during the day. A diagnosis of hypothyroidism can be ruled out if the TT4 is in the upper 50% of the lab’s reference range. Autoantibodies to T4 which occur in approximately 10–15% of hypothyroid dogs may falsely elevate the serum T4 concentration from below normal into the normal range so the T4 antibodies need to be interpreted with the TT4.

2. Serum Free T4 (FT4)

Since T4 is highly protein-bound in the circulation and can be altered by many non-thyroid illnesses and by certain drugs, measurement of the inbound or free T4 can provide a more accurate assessment of thyroid function. ***Measurement of fT4 by equilibrium dialysis should be performed when uncommon clinical signs of hypothyroidism are present, the dog is being treated with a drug that may affect thyroid function, when non-thyroidal illness is present, and if autoantibodies to T4 are detected.

3. Serum TSH

Primary hypothyroidism results in a decrease in T4 with decreased negative feedback causing the pituitary gland to secrete more TSH (thyroid stimulating hormone). Serum levels of TSH increase as more thyroid hormone is needed. In the dog, TSH concentration is elevated in 65–75% of cases of hypothyroidism so it cannot be used as a single screening test. ***25–35% of dogs with hypothyroidism have normal TSH.

4. Thyroid Autoantibodies

Antibodies against T4 or T3 or both are sometimes present in dogs with autoimmune thyroiditis. The presence of these antibodies does NOT indicate that the dog is hypothyroid, but suggests that autoimmune thyroid disease is present. ***Autoantibodies frequently cause false elevation of T4 or T3 making it confusing and difficult to interpret these numbers. Dogs with autoimmune thyroiditis have circulating antibodies to thyroglobulin, the primary protein making up the colloid of the thyroid gland. ***TGAA (thyroglobulin autoantibodies) is a measurable marker for the presence of immune-mediated thyroid disease. More than 60–70% of the thyroid tissue needs to be destroyed before changes occur in laboratory measures of thyroid function. The majority of dogs that develop autoantibodies do so by 3–4 years of age. Development of high levels of autoantibodies at any time in a dog’s life is an indication that the dog most likely has the genetic form of thyroid disease. ***In a longterm study at Michigan State University, 20% of asymptomatic, anti-thyroglobulin positive dogs with normal thyroid function progressed to hypothyroidism in one year.

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There are currently THREE MAIN INDICES that determine the OFA Thyroid Classification:

The metabolically active fraction of T4 is considered the “gold standard” for assessment of the thyroid’s production and cellular availability of thyroxine. It is less affected by nonthyroidal illness and drugs than TT4. Measurement of fT4 should be done by equilibrium dialysis expecting results to decrease in dogs with thyroid dysfunction due to autoimmune thyroiditis

2. Canine Thyroid Stimulation Hormone (cTSH)

cTSH helps determine the site of the thyroid pathology: autoimmune thyroiditis — the lesion is at the level of the thyroid gland and the pituitary gland in the brain functions normally. cTSH is expected to be elevated in dogs with thyroid atrophy from autoimmune thyroiditis

3. Thyroglobulin Autoantibodies (TGAA)

Elevated TGAA is an obvious confirmation of immune-mediated thyroid disease. Antibodies against thyroglobulin are produced during the disease process of lymphocytic thyroiditis. ***In some animals this process never progresses to cause clinical disease. ***Because of the known hereditary component to the development of thyroiditis, measuring TGAA is used to identify animals predisposed to hypothyroidism prior to breeding before clinical signs have developed.

Looking at thyroid profiles, certain breeds have normal ranges of thyroid hormones that are different from most other breeds. Few have been specifically evaluated, but Sighthounds (Greyhounds, Scottish Deerhounds, Salukis, Whippets) have serum TT4 and fT4 concentrations that are considered lower than most other breeds. Lower T4 concentrations are also seen in normal Alaskan sled dogs.

When interpreting thyroid profile results, the dog’s clinical presentation and the possibility of Euthyroid Sick Syndrome must be considered. It is well documented that thyroid hormone concentrations can decrease as part of a metabolic response to nonthyroidal illness.

Alternative Explanations for decreases in thyroid laboratory values

Seizure medications, prednisone, or other corticosteroids- including topical medications for eyes and ears, NSAIDS or nonsteroidal anti-inflammatory drugs used for injury or arthritis pain like Deramaxx or Rimadyl (carprofen) , separation anxiety medication like clomipramine can all contribute to lower thyroid hormone numbers. Sulfonamide antibiotics, sometimes prescribed for urinary tract disease, can actually trigger a “reversible” hypothyroid state with numbers returning to normal after withdrawing medication. Physiologic adaptations to decreased cell metabolism during periods of illness cause changes in thyroid hormone production, the characteristics of serum protein binding, and the altered metabolism of thyroid hormones which may all contribute to the false low results. Despite low numbers, the dog remains euthyroid or normal at the cellular level and should NOT be treated. More than 60–70% of the thyroid tissue needs to be destroyed before changes occur in laboratory measures of thyroid function. This process can take months or years to cause classic hypothyroidism. *** In some dogs, it may not progress.

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Treatment is usually simple with medication

Treatment for Hypothyroidism

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TAKE HOME POINTS for GWP OWNERS:

  • Canine hypothyroidism is heritable, so knowing the status of a dog and the status of the dog’s lineage allows breeders to decide which matings are most appropriate for reducing the incidence of autoimmune thyroiditis in GWP offspring. ***Laboratory and pedigree analyses of affected families show a progressive earlier age of onset of thyroiditis and clinical signs of dysfunction, as well as an increased portion of affected vs normal offspring in successive litters.
  • Breeding normal testing dogs that have come from litters which have mostly tested normal is recommended. ***Always retest equivocal results. Testing is not simple or perfect. Discordant test results are common and retesting can be required
  • Ruling out hypothyroidism as a contributing factor to aggression, “irritability”, and abnormal behavior is valuable.
  • It would be interesting to analyze our GWP data checking trends in our TT4, fT4, numbers as a “group.”

Email Robin K Nelson at gwpoint@aol.com with any questions

References:

  1. Hanseltine, Johanna. Canine Hypothyroidism: Diagnosis and Treatment. TVP March/April 2019
  2. Dodman, NH, Miczek, KA, Knowles, K, Thelhammer, JG, Shuster, L. Phenobarbital-responsive episodic dyscontrol (rage) in dogs. JAVMA Vol 201 No 10 Nov 15 1992 1580–3
  3. Aronson, LP, Dodds, W. J. The Effect of Hypothyroid Function on Canine Behavior. Pet Shrink 2008
  4. Landsberg, GM. Is It Medical or Is It Behavioral? Companion Animal Behavior Therapy Study Group 2008
  5. Peterson, M. Hypothyroidism in Animals. Merck Manual 2019
  6. Leviton, D M. Canine Hypothyroidism — Are You Over Treating? Atlantic Coast Veterinary Conference 2016
  7. Horowitz, D, Lansbury, G. Puppy Behavior and Training- Socialization and Fear Prevention. Behavior Pet Services
  8. Shell, L, Rothrock, K. Hypothyroidism, Acquired. Vincyclopedia of Diseases 2018
  9. Please refer to Dr Sharon Albright’s article Spring 2020 Wire~News page 17 for the latest research regarding new test method development for Canine Hypothyroidism.
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About Us

Working hand- in-hand with governmental and local shelters, NGWPR provides a safe and responsible home for GWP’s in need. Placed with an experienced GWPCA member, fostered GWPs that have been neglected, untrained or have medical issues quickly blossom as they are readied for their “forever” homes.

Prior to releasing our rescued GWPs for adoption, volunteers provide obedience, manners, and house training. We hold to the philosophy that a mannerly dog has a better chance of fitting into a new household.

NGWPR believes that Wires were designed to hunt and unlike some other rescue programs, we are happy to place dogs with field experience or bird instinct with potential owners who enjoy hunting behind a Wire. However, NGWPR insists that any rescue dog first be a house dog and companion, then a weekend hunting partner.

Please go to our website to learn more.

http://www.nationalgwprescue.com/

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Click here to donate to NGWPR

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We believe that the more we educate people the more likely we are to accomplish our mission of matching homeless GWPs with loving owners.

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