Has Your Hypothyroid Hound Had Neuro Symptoms?

[mrsmcd7]

Max's T4 is less than 0.50 so they're running a panel. Anyone with a hypothyroid hound? I know that can be normal for a lot of hounds but I'm wondering what symptoms your hypothyroid hounds have displayed, especially neurologically and what their T4 was that the vet decided to treat.

[macoduck]

By panel, do you mean the full thyroid panel rather than just a T4?

[mrsmcd7]

Yes

[tbhounds]

Yes

Ghs typically willl run low on not only T4's but the Ft4 may be low too--gotta check that cTSH ;-)

[dmswartzfager]

While I have not yet seen a greyhound with hypothyroid-induced neurologic signs (but I've only been a neurology tech for just over a year now...), I was surprised to learn that our neurologists will run a Michigan State thyroid panel on dogs that present with vestibular disease, and other neurologic signs that don't have an obvious cause. Most thyroid panels will come back normal, but some don't, and the dogs usually do better once thyroid supplementation starts.

 

I'd be happy to pull together references, if you're interested.

[RaineysMom]

Our Rainey was Dr. Couto's "fourth" truly low thyroid greyhound (back in 2010). In August of 2010, just before turning 10 she began having seizures, and in November she tested truly with a low thyroid. I do not think this had anything to do with the seizures (although she was put on meds for it, and it didn't change the seizures) but since you asked I thought I'd mention....

[mrsmcd7]

Thanks all. His behavior is strange. Panting and Pacing in the evenings and just wanting to lay down outside a lot which he never has before. Almost like sundowners in dementia.

Ghs typically willl run low on not only T4's but the Ft4 may be low too--gotta check that cTSH ;-)

Panel for humans include antithyroid antibodies, Free T4, tsh, t3. I would assume canine panel would be similar. It's expensive. $200.

Ghs typically willl run low on not only T4's but the Ft4 may be low too--gotta check that cTSH ;-)

Panel for humans include antithyroid antibodies, Free T4, tsh, t3. I would assume canine panel would be similar. It's expensive. $200.

[mrsmcd7]

While I have not yet seen a greyhound with hypothyroid-induced neurologic signs (but I've only been a neurology tech for just over a year now...), I was surprised to learn that our neurologists will run a Michigan State thyroid panel on dogs that present with vestibular disease, and other neurologic signs that don't have an obvious cause. Most thyroid panels will come back normal, but some don't, and the dogs usually do better once thyroid supplementation starts.

 

I'd be happy to pull together references, if you're interested.

I would really appreciate that!

[dmswartzfager]

I would really appreciate that!

 

You got it. I'm heading out for the day, but I'll start working on it later this evening.

[dmswartzfager]

From NeuroPetVet, written by Dr. Mark Troxel, one of the big names in veterinary neurology...

 

Hypothyroidism

Hypothyroidism is one of the most common endocrine disorders encountered in dogs. The reported incidence ranges from 0.2 to 0.8% of the canine population. Clinical hypothyroidism results from low triiodothyronine (T3) and thyroxine (T4), the active thyroid hormones produced by the thyroid glands. Primary hypothyroidism accounts for 95% of cases and is most commonly due to lympocytic thyroiditis or idiopathic thyroid atrophy. There are many other reported causes, but the incidence is very low. For an in-depth review of this condition, please consult an endocrine textbook or see the articles listed at the bottom of the page.

Signalment

Hypothyroidism is most common in middle-aged to older dogs. Approximately 1/3 of patients have onset of clinical signs between 4 and 6 years of age, while approximately 22% of cases each occur from 2-4 years of age or 7-9 years of age. Congenital hypothyroidism is rare in dogs. Clinical hypothyroidism is also uncommon to rare in cats.

Clinical signs

Hypothyroidism causes a wide range of clinical signs affecting multiple body systems. Common clinical signs include weight gain, lethargy, mental dullness, skin disorders (hyperkeratosis, symmetric alopecia, thin hair coat, seborrhea, hyperpigmentation, etc.), gastrointestinal disease (e.g., esophageal hypomotilitiy), cardiovascular dysfunction (e.g., bradycardia), neuromuscular disease, reproductive problems and many others. A cause-and-effect relationship has not been established for most of the disorders listed below, and some of the conditions that have been “linked” to hypothyroidism are controversial.

PERIPHERAL NERVOUS SYSTEM DYSFUNCTION ASSOCIATED WITH HYPOTHYROIDISM

Cranial nerve dysfunction

Hypothyroidism has been associated with peripheral cranial nerve dysfunction of several cranial nerves, most commonly the facial nerve, vestibulocochlear nerve, and sensory branch of the trigeminal nerve. Facial nerve paralysis has been reported in up to 70% of dogs with clinical hypothyroidism and nerve dysfunction. Clinical signs of facial nerve paresis / paralysis include drooping ear, facial droop, inability to blink, and decreased tear production.

Peripheral vestibular dysfunction

Peripheral vestibular dysfunction has been linked to hypothyroidism. Clinical signs include head tilt, horizontal or rotary nystagmus, and vestibular ataxia. The vestibular signs may resolve in time, but recovery may take several weeks after beginning thyroid hormone supplementation.

Laryngeal paralysis

Hypothyroidism can be a cause of laryngeal paralysis. In one study, 30 of 140 dogs with laryngeal paralysis had concurrent hypothyroidism. There is little information in the veterinary literature regarding treatment and recovery from laryngeal paralysis in hypothyroid dogs. Most consider laryngeal paralysis to be a surgical disease, but hypothyroidism should be treated nonetheless.

Megaesophagus

Hypothyroidism is commonly listed as a possible cause of megaesophagus in dogs. However, recent studies suggest this may not necessarily be true.

Myasthenia gravis

Concurrent myasthenia gravis and hypothyroidism has been reported in dogs. In human medicine, approximately 10-20% of myasthenic patients have concurrent thyroid disease. Some speculate that there is cross-reactivity between anti-acetylcholine receptor antibodies and thyroid antigens.

Polyneuropathy

Hypothyroidism has been associated with a generalized polyneuropathy in dogs, most commonly in large and giant breed dogs. Clinical signs are typical of a generalized neuropathy, including generalized weakness, postural reaction deficits, hyporeflexia, decreased muscle tone, and muscle atrophy. Electrodiagnostics and nerve/muscle biopsy are occasionally performed, but laboratory testing often negates the need for these tests. Clinical signs often improve quickly with thyroxine supplementation and many dogs recover fully within 1-2 months.

Myopathy

Hypothyroid dogs may show signs of a generalized myopathy, including generalized weakness, stiffness, and muscle pain. The incidence in dogs is uncertain, but up to 40% of humans with hypothyroidism has skeletal muscle weakness.

CENTRAL NERVOUS SYSTEM DYSFUNCTION ASSOCIATED WITH HYPOTHYROIDISM

Central vestibular dysfunction

Hypothyroidism is most commonly associated with peripheral vestibular dysfunction, but it has also been reported in dogs with central vestibular dysfunction. There are only a handful of cases described in the veterinary literature, with several of the dogs having an infarction

Seizures and other forebrain signs

It is unclear if there is truly a direct cause-and-effect relationship for hypothyroidism as a cause of seizures. It’s been hypothesized that hyperlipidemia and atherosclerosis that occurs with hypothyroidism may be the cause of some patients’ seizures, as well as other forebrain signs, such as mental dullness, behavior change, and compulsive circling. It is also possible that hypothyroidism exacerbates seizure activity, making it more difficult to control seizures, rather than being a direct cause of seizures. In one retrospective study of 96 dogs with metabolic or toxic causes of seizures, only 3% of the dogs were hypothyroid. This finding, however, is limited by the retrospective nature of the study and the fact that there was little information provided about the hypothyroid dogs.

Myxedema coma in a Labrador Retriever with severe hypothyroidism. Note the edematous lips and eyelids. The dog was stuporous upon presentation to the hospital. He improved quickly after being given IV levothyroxine and returned to normal over the following 2 weeks with oral levothyroxine supplementation.

Myxedema coma

This is a rare manifestation of severe hypothyroidism in dogs that may be the result of abnormal neurotransmitter release/uptake or failure of thyroid hormone to enter the brain. Common clinical signs are thickened skin due to accumulation of mucopolysaccharides and hyaluronic acid, which bind water leading to pitting edema of the face, bradycardia, and stupor to coma.

Diagnosis

The “classic picture” of hypothyroidism is low serum total T4 and free T4 levels and elevated TSH levels, especially when combined with compatible clinical signs. Nonregenerative anemia and hypercholesterolemia help further support the diagnosis.

Screening total T4 is commonly performed, often as part of a “package” including a CBC & biochemical profile. Normal total T4 means that the patient is almost certainly euthyroid. However, low total T4 may be due to hypothyroidism or euthyroid sick syndrome, a condition characterized by low total T4 and/or free T4 secondary to non-thyroidal illness or stress. Free T4 is the most accurate test of thyroid function if only one test can be performed. If the TSH level is high in patient with low free T4, hypothyroidism is likely. However, TSH alone cannot be used as an indicator of hypothyroidism as 20% of hypothyroid dogs have a low free T4, but a normal TSH level.

Treatment

Hypothyroidism is treated by supplementation with levothyroxine. The starting dose is 10-20 µg/kg (0.01-0.02 mg/kg) PO q12hr. The T4 level should be measured 4 weeks later 4-6 hours post-pill. Myxedema coma should be treated intravenously (5 µg/kg IV q12hr) since levothyroxine may not be well-absorbed orally in these patients.

Prognosis

The prognosis for recovery is generally good, but it may take several weeks to months to recovery fully.

[dmswartzfager]

http://www.geac.ufv.br/n52006-Neuromuscularmanifestationsofhypothyroidism.pdf

 

http://veterinarymedicine.dvm360.com/hypothyroid-associated-neurologic-signs-dogs

 

http://onlinelibrary.wiley.com/doi/10.1111/j.1939-1676.2006.tb00752.x/full

 

http://onlinelibrary.wiley.com/doi/10.1111/j.1939-1676.1994.tb03245.x/full

 

 

In my brief glance through those articles, I'm not seeing anything that specifically mentions a link between hypothyroidism and what you are describing, but I'll keep looking, and if we have time between appointments tomorrow, I'll ask my neurologists.

[mrsmcd7]

Thank you so much!! Very helpful.

[NeylasMom]

Thanks all. His behavior is strange. Panting and Pacing in the evenings and just wanting to lay down outside a lot which he never has before. Almost like sundowners in dementia.

 

Panel for humans include antithyroid antibodies, Free T4, tsh, t3. I would assume canine panel would be similar. It's expensive. $200.

 

Panel for humans include antithyroid antibodies, Free T4, tsh, t3. I would assume canine panel would be similar. It's expensive. $200.

How old is he? Is it possible he's beginning to have some CCD symptoms?

 

And yes, a good thyroid panel will have all if those things for dogs. I usually request my vet send blood to MSU. You can download the order form and the shipping instructions from their website to give to your vet and then they ship directly to them. The results will include an interpretation from one of their scientists (you may have to pay a small fee to add this on, around $8 I think). But if your vet has already sent it to another lab it should be fine.

[mrsmcd7]

He just turned 9

[GeorgeofNE]

I wouldn't rely on general articles on thyroid issues in dogs.

 

We all know greyhounds are not normal when it comes to thyroid issues.

[mrsmcd7]

Panel came back and all other thyroid tests are normal so he has the typical low T4 of the breed. Yay!