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What is Thyroid Poisoning?

Thyroid hormones are a vital part of the day to day function of the body. Heart rate, body temperature regulation, and oxygen consumption are just a few of the systems that work in sync with the thyroid. Thyroid problems in animals and people are not uncommon making this type of medication a normal item in the medicine cabinets of many households. Whether your pet gains access to your supply of medication or if you accidentally give him to much of his own prescription, veterinary care will be needed to ensure your pet remains in good health. Studies show that canines can function quite well and have a high margin of safety when it comes to overdose. However, toxicity from the consumption of a very large amount is possible, though rarely documented in veterinary literature. A few of the symptoms of toxicity can be tremors, vomiting,and diarrhea. Treatment is necessary in the case of severe poisoning, and may include medication that must be administered in a hospital setting in order to control symptoms.

Dogs and humans both can be prescribed thyroid hormones for conditions such as hypothyroidism. The hormone levothyroxine (a synthetic form) is the typical choice for treatment in canines and humans alike. Overdose of this hormone can cause toxicity in your pet.

Thyroid Poisoning Average Cost

From 66 quotes ranging from $300 - $3,000

Average Cost

$750

Symptoms of Thyroid Poisoning in Dogs

Symptoms of thyroid poisoning in dogs may appear between 1 and 9 hours after the pills were ingested. A mild case of toxicity will involve hyperactivity and an increase in heart rate. The ingestion of a large number of thyroid pills may mean the following symptoms can appear.

  • Excitability
  • Nervousness
  • Excessive panting
  • Lethargy
  • Vomiting
  • Diarrhea
  • Abnormal reflex of pupils to light
  • Contraction of the pupils
  • Tremors of muscles
  • Rapid heart rate
  • Rapid breathing
  • Difficulty breathing
  • Aggression

Types

Toxicity to thyroid hormones is typically an acute event, meaning it occurs as the result of a large ingestion of pills. Chronic overdose can occur over time; though studies show that the liver and kidneys can handle and disperse the hormone well even in cases of overabundance. There is also evidence that thyroid hormones have a slow gastrointestinal absorption allowing for a period of toxicity that is not apparent right away.

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Causes of Thyroid Poisoning in Dogs

  • Dogs can tolerate and in fact, need a higher dose per weight than humans do in order for the hormone to do its job
  • An enzyme in the liver (alanine transaminase) has increased activity; this is why underlying liver issues can exacerbate the poisoning
  • Symptoms will vary in dogs but are most commonly mild to moderate; severe toxicity is rare
  • Medications may react adversely to an excess of the hormone
  • Concurrent heart problems can make thyroid hormone toxicity more symptomatic
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Diagnosis of Thyroid Poisoning in Dogs

As with any poisoning by medication or substance that is known to be dangerous when ingested, bring along the container or packaging that contained the thyroid hormone pills as this will be helpful for the veterinarian to see. If you have an idea of the time of ingestion this is important information to relay to the veterinarian because whether or not the team induces vomiting depends on the timing (less than 2 hours prior).

Clinical signs relevant to thyroid poisoning will be considered as the physical examination takes place. Your dog’s heart rate and blood pressure will indicate how severe the toxicity is and blood work will reveal T4 levels and other markers like electrolytes and liver enzymes. The treatment protocol will be determined by the level of poisoning indicated in the diagnostic process.

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Treatment of Thyroid Poisoning in Dogs

A pet who has experienced significant toxicity due to thyroid hormones will be hospitalized. Fluid therapy will be commenced to aid in the administration of  medications for nausea, vomiting, or diarrhea if needed. Additional drugs could include those meant to regulate symptoms like a rapid heart rate and uncontrollable tremors, and those which will help to eliminate the excess thyroid hormone from the system. 

If emesis is within the two hour time frame, this will be initiated along with other gastric decontamination measures such as activated charcoal administration. Oxygen therapy will be provided if beneficial; at the same time the fluid therapy may be slowly continued and the heart activity will be closely watched.

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Recovery of Thyroid Poisoning in Dogs

A dog without underlying conditions and who has been treated in a timely manner will have a good prognosis for recovery. Once your pet has been released from the care of the veterinarian, he can return home provided that he has a comfortable, quiet resting place. Continue to monitor him at home and be certain to contact the clinic if your dog’s behavior changes in any way that causes you concern. For the future, keep all medications, dangerous substances, household products, and forbidden food out of reach of your pet and if you have in your possession medication prescribed for your dog, follow the instructions very carefully.

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Thyroid Poisoning Average Cost

From 66 quotes ranging from $300 - $3,000

Average Cost

$750

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Thyroid Poisoning Questions and Advice from Veterinary Professionals

Need pet health advice? Ask a vet

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Ask a Vet

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Australian Cattle Dog

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Seven Months

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Unknown severity

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0 found helpful

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Unknown severity

Has Symptoms

None Yet

My puppy ate my whole prescription of thyroid medication. They were 50mcg and there was 90 of them. I’m not sure what to do.

Sept. 29, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. I'm not sure if your medication was for an increased or decreased thyroid condition, but regardless, your puppy needs to go to the ER to be treated. I hope that all goes well for your puppy.

Oct. 3, 2020

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Chihuahua pug

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Seven Years

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Unknown severity

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Unknown severity

Has Symptoms

Not Eating The Same

Teddy has been diagnosed with thyroid’s and has been on medication for two months haven’t got the right doses yet but he is losing weight and has more energy but his eating habits have changed he’s very finicky doesn’t eat like he used to

Sept. 28, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. Decreased appetite doesn't usually have much to do with thyroid disease, and I suspect he may be getting picky for other reasons. If you are feeding him table food, or if he has food available all the time, those things can make dogs more picky. If changing those things to where he doesn't get table food, and he is fed twice daily don't help, then following up with your veterinarian might be a good idea. I hope that all goes well!

Oct. 4, 2020

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Brittany (Spaniel)

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Fourteen Months

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Unknown severity

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Unknown severity

Has Symptoms

None

My 38lb dog took 0.8mg synthroid (another dogs medication). She took it approximately 35 minutes ago and is not having any symptoms. My vet isn’t open with it being a holiday weekend, do I need to take her to an emergency vet?

Sept. 6, 2020

Owner

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Dr. Kate D. MA VetMB MRCVS

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Hello, Thanks for contacting us about your dog. A single dose of 0.8mg synthroid for a 38lb, otherwise healthy dog should not be too much of a problem and may not cause any symptoms. However, if you are in any way unsure of how many tablets she took, or if she has any health conditions of her own, I would strongly advise you contact the emergency clinic as soon as possible to discuss with them. You have done the right thing in reaching out for advice really early, and if the emergency vets felt it was necessary there is still opportunity to help her vomit up the medication if she gets to the clinic within a couple of hours of eating them. I hope that helps.

Sept. 6, 2020

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Terrier mix

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Five Years

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Unknown severity

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No Symptons

My sons dog ate a .8 mg levothyroxine tablet for my dog by accident...can that harm her? Should I do anything?

July 27, 2020

Owner

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Dr. Michele K. DVM

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Thank you for your question. It is hard to say without knowing how much your son's dog weighs, but there is a wide safety range for that drug. I wouldn't imagine that a one-time dose would hurt your son's dog, but if you are not sure, it would be best to either call your veterinarian or an emergency clinic near you, or a pet poison hotline. You can give them the weight of the dog as well as the medication strength, and they can let you know if there's a problem. I hope that all goes well.

July 27, 2020

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Pitt

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Five Years

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Unknown severity

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7 found helpful

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Unknown severity

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N/A

Accidentally gave dog an extra thyroid pill

July 26, 2020

Owner

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Jessica N. DVM

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7 Recommendations

Hello- Thank you for your question. A second dose of thyroid medication should not be toxic for your dog. I would just recommend skipping his next dose this evening and waiting until tomorrow to resume the medication on a normal schedule. Have a good day.

July 26, 2020

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Max

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Siberian Husky

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7 Years

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Critical severity

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Our 7 1/2 year old Siberian Husky was diagnosed with hypothyroidism after a blood work. He weighed about 92 - 94 pounds, was lethargic, thinning of hair, with dull and brittle hair. Our vet prescribed .8 mg of Tyhro-tabs, 2 times daily, so a total of 1.6 mg a day. At first he seemed more perky, with more enegry. After 10 days on the medication, he stop eating, began to drink a lot more water and didn't have as much energy. He also had diarrhea a couple times on the 2n day of not eating. We took him to the Pet Emergency, they gave him Metronidazole, 500 mg, 2x daily. Took our dog to our vet 2 days after the Pet ER, our dogs temperature was 104.5, still some diarrhea and vomited once. Vet prescribed Amoxicillin, 3x daily, and indicated to continue with the Metronidazole, and cut the Thyro-tabs to .4mg every 12 hours, even though she thought it wasn't the Thyro-tabs causing our dog to not eat, drinking a lot, high temp, diarrhea, and vomiting once. Went back to the vet the next day and the et did X-rays, more blood work and a urine test, at this visit his temp was 105.4. They also gave him fluids under his skin on his back to rehydrate and cool him down. We have not be able to get our dog to take the medicine regularly, and more often not. Even the vet couldn't get his meds in him while they had him for 1/2 a day for the X-rays and blood work. Our dog hasn't eaten a meal for 7 days. Only little bits of turkey lunch meat to try to get him to take his pills. But he has stop even taking the pills with the turkey (which he usually loves the turkey, but hardly ever gets since we try to keep him on his regular dog food. But at this point w were willing to let him eat just about anything if it would help him take his pills and the vet said to give the pills with food he loves to eat. We've even tried a pill dispenser (popper), but that didn't work. Since he was drinking so much water, we even tried beef broth to try and get some liguids with a little nutrients in him, but he smelled but would driink any of it. I asked our vet if the .8 mg 2x daily was too high of a dose and could our dog be having an adverse reaction and/or now have Thyrotoxicosis, but the vet indicate no, she didn't believe so, that the high fever is not an adverse side effect of the Thyro-tabs. From the X-rays the vet said the stomach was very enlarged and so were the intestines and they believe it is gastrointestinal cancer, and that was also probably contributing to the low thyroid issue. The vet said to stop the Thyro-tabs and focus on the Metronidazole, she added Cesernia (spelling - for nausea for 4 days) and Mitrazine (appetite stimulant for 7 days), and 1/2 imodium AD (for 3 days) to see if we can get his intestines not so inflamed so our dog may be willing to eat. But almost no luck in getting the pills into him. The vet also said with treatment for the cancer, it would only give our dog about 2 - 6 months more time, but he would have to take some more pills to stay comfortable and hopefully so he'll eat. If it was the Thyro-tabs that caused the initial problems, how long after being off of the Thyro-tabs would you think it would take for our dog to start eating again? The vet has recommended that it would be best for our dog to be put to sleep, as he can't be comfortable since he won't eat and/or take the pills. We have a vet coming to our home tomorrow to put him to sleep. It is breaking our hearts, we love him so much, he's part of the family, but don't want him to suffer. He is such a sweet dog and so loving, we feel we have to do whats best for him. But I feel so unsure, it just seems such a coincidence that only after 10 days of being on the Thyro-tabs that this all started. But 3 vets within the same practice have indicated they don't think it is the Thyro-tabs and/or the dosage amount. Don't know what else do to four our dog, put he can't go on this way without eating, he looks so sad when he looks at you now, like he's saying please help me. He hasn't been taking the Thyro-tabs for a few days and we had reduced it to .4 mg for a few days before that. I keep hoping each morning that we see improvement in him, but it seems to being getting worse, and more weak by the day. Please respond even if it doesn't help us, in case others have this same experience they may know how and who to reach out to get better way to get it fixed.

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Dotty

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Whippet

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9 Years

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Serious severity

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Serious severity

Has Symptoms

Shaking
Lethargy
Head Tilt
Difficulty Walking
Tremor
Stiff Joints

I took my nine year old whippet to the vet a month ago because she has put on some weight over the years. They did bloodwork and the vet said she had a slow thyroid so she put her on .4mg of thyrosyn twice a day and she weighs 37 lbs. She has been acting fine for the past 4 weeks but last night she totally changed and not in a good way. It was like her joints locked, she won't walk, she is not attentive, and will not even look at me. Her whole body is shaking and trembling. She will not eat on her own, I have to feed her piece by piece by mouth. I try to set her up on her feet and she will walk very slow but then just lay down on the ground and not move. This is very alarming for me.

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Gianni

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Silky Terrier

dog-age-icon

13 Years

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Moderate severity

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pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

Has Symptoms

Lethargy
Frequent Urination
Excessive Thirst
Panting
Hind Leg Weakness
Zoning Out

My "Puppy" is 13 years young... was in perfect health as far as I knew -still running around playful and active, sleeping a little more than he used to but it seemed age appropriate. I took hi to the vet for routine check up. Vet called after visit and advised that his thyroid level was very low, below .5, and that I needed to put him on thyroid meds right away. My boy is a silky terrier, weighed at the time 11 pounds. Vet prescribed .2mg of thyroxine. Suddenly he was very lethargic - less playing, poor coordination, just not who he was. After 3 weeks he then had a shift - acting playful again - jumped up on the bed which he hadn't done in a long time... it has all been one thing after another since then... he started increased panting - even in his sleep, he seemed way too amped up... I researched that the dosage was high and I started giving him 1/2 the pill each day (.1 total for day) I called vet and he said bring him back in to retest - said I should give him .1 2x a day... I reluctantly did this and then brought him in a few days later - Test showed He was then at the high end of normal range. Vet then says something about his elevated liver levels - which he NEVER mentioned. I picked up all copies of blood tests and went to another vet. The new vet put him on .1 2 x a day and retested liver as well - which now (1 month after initial test) has doubled. After 3 weeks we retested his thyroid and he did an abdominal sonogram. Said the liver was ok except for a bright area which could be from age, said something about his adrenal glands (wish I could remember!!! I am waiting for a call from him now), now he also noticed a heart murmur and his liver levels are now I believe 365- up again. He put him on Denamarin. I read online that home cooked food would be better for him than the Blue Buffalo he has been eating for the last 2 years - and I stopped the cosequin he had everyday... I started giving him boiled chicken, brown rice, raw spinach, sometimes adding nonfat cottage cheese and sweet potato. This was last week... now... panting started to return, a little bit of jaw chomping (for a short period) - lethargic, indifferent, not wanting to play - seems to have ups and downs, drinks more water than normal. Then suddenly 3 days ago he started having accidents. He urinated on the floor 3 times in one day - and this was with walks in between. He NEVER urinated on the floor in the night before - now he has for the last 2 nights in a row. The vet said drop the dose to .05 2 times a day. First such dose was last night. This morning he drank excessively - then vomited (all clear and undoubtedly the water he gulped down), then he urinated on the floor again and had diarrhea.... How I wish I never started any of these medications - he was absolutely fine!!! I just want my boy back to normal - he just sleeps at my feet for most of the day... he is like a wet noodle. Weighs 10 lbs now. When I spoke to the vet yesterday he mentioned something about cushings... I am getting info in dribs and drabs - everything seems like speculation.... can anyone offer me some insight here - this little boy means the world to me....

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Penny

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Rat Terrier

dog-age-icon

9 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Serious severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Serious severity

Has Symptoms

Weight Loss, Excessive Hunger,Hyper

My dog shows every symptom of hyperthyroidism, but my vet diagnosed (through blood work) hypothyroidism and put her on thyro tabs 0.1 mg twice a day. I'm afraid to start this med due to already significant weight loss. Any thoughts on this please!

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Daisy

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German Shepherd

dog-age-icon

6 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Fair severity

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1 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Fair severity

Has Symptoms

Heavy Breathing, Weird Behavoir

I have a 5-6 year old german mix rescue. She (Daisy) has gained A LOT of weight in the last year. Took her to the vet and her blood test indicated-low thyroid. It's been about two weeks I am giving her 2 pills (my pups ate the pill bottle) twice a day. I have noticed her personality change. She has become aggressive toward my other dog (Chance). He is somewhat equal to size but he was been with her since he was 9 weeks old. She has not become aggressive to my 2 smaller fosters. I have been keeping her in my room and walked in and found her licking all over the floors-just walking around licking. So weird - she had water and never has done that. I am convinced its the meds. Has anyone else experienced this?

Thyroid Poisoning Average Cost

From 66 quotes ranging from $300 - $3,000

Average Cost

$750

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