How is unabsorbed T3 excreted from the body? - Thyroid UK

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How is unabsorbed T3 excreted from the body?

milupa profile image

Hi everyone - I am still trying to figure out what causes my super hyper 14 months old dog’s low TSH (0.02, no low range given for dogs) and above range T4 4.46 (2.2 - 4.2).

My only explanation is that he somehow (skin) gets T3 from my husband or me, we are both on T3 only.

The most obvious answer (that he has a thyroid problem) is dismissed by the vet who claims that dogs cannot develop hyperthyroidism.

I am generally curious as to how T3 is metabolized in the body. Any ideas? Thank you.

12 Replies

Hi milupa. I would find a different vet! It's more common for dogs to be hypo and cats to be hyper, but it's certainly possible for them to develop the opposite thyroid condition to the one expected. Your dog's results are a bit over range, but not wildly so. In my experience as custodian of a hyper cat, it can be very difficult to persuade vets to carry out a full range of tests in cases that are not clear cut, even when you wave your credit card at them.

As for absorption of T3 via skin contact, I suppose it's theoretically possible, but I've no idea whether it's actually likely. Anyone...?

Hillwoman profile image
Hillwoman in reply to Hillwoman

I've just remembered that a doctor I know (Sarah Myhill) was thinking of developing a T3 medication that could be absorbed through the skin, but it would have to be in a vehicle that could penetrate the skin barrier, probably DMSO.

milupa profile image
milupa in reply to Hillwoman

Dr Myhill is just fabulous, isn’t she? Are you lucky enough to be one of her patients?

Regarding vets: It’s been a steep learning curve since I got the pup a year ago. His thyroid numbers were off even at five months old. He has an autoimmune eye condition which might be the result of high cortisol levels but they won’t test for that. He has spinal problems as well plus allergies. I feel so sorry for him.

I hope your cat is as well as she can be with you looking after her so well!

Hillwoman profile image
Hillwoman in reply to milupa

Yes, I've known Dr SM a very long time, though there was period of about 18 years in the middle when I was under another doctor's care because we moved to a different region. Luckily, I was still her patient in formal terms so was able to resume with her (long distance!) when my other doctor retired.

I'm worried about your dog, and would really urge you to find a holistic vet. There are some dotted around the country, but I'm afraid I've lost the details. Try Google?

milupa profile image
milupa in reply to Hillwoman

Dear Hillwoman - super that you are one of her patients! I just study her website :-(

Thanks for the encourgement, I wanted to use holistic vets from the start but no luck (in Berlin). My dog sees a chiropractor who is also a homoeopath. But by now I feel like I have to protect him from vets. A bit like I have learned to question what my own docs say!

Hillwoman profile image
Hillwoman in reply to milupa

Sadly, that's the conclusion we've reached with our cat. We used to have an old school vet who would offer to give her a B12 jab to perk her up, and generally pay attention to her rather than the blood test results. Younger vets under 45 are now just as rigid and fearty as human doctors.

Dr M's website is an excellent resource, as are her books, so you can still access her distilled experience that way. Still, I'm very glad to have her personal input, and I know I'm very lucky.

Of course dogs and cats can develop hyperthyroidism. I've know two hyper cats who needed partial thyroidectomy. T3 absorption through undamaged skin - not. T3 is degraded to T2 then to T1 then to iodate and is either excreted in urine if in excess or recycled to the salivary glands for reuse by the thyroid building up T4 and T3 again for reuse.

milupa profile image
milupa in reply to diogenes

Thank you so much for your answers!

My dog (Boston Terrier) only ever calms down when he has body contact with me, so I am glad I don’t have to ban him from curling up on the couch with me.

I guess I’ll be battling vets as well as GPs and endos from now on (dog seems to have as many health issues as I).

Some info that may help you to push things further with the vet:

Hyperthyroidism is a very rare condition in dogs and when it does occur, is usually caused by an aggressive thyroid tumor. That’s why three recent studies linking the disease in a handful of dogs to their raw diets are worth mentioning.

Hyperthyroidism is a condition in which the thyroid glands over-produce thyroid hormone, causing a constant state of metabolic hyperactivity. Clinical signs include increased thirst and appetite, excessive urination, vomiting, weight loss, and increased heart rate. Left untreated, the condition can cause heart and kidney failure.

In three recent studies, a small number of dogs were diagnosed with dietary-related hyperthyroidism caused by ingesting active thyroid tissue contained in raw diets. Gullets, head meat, and animal necks were the suspected culprits.

While the studies involve a very small sampling of raw fed dogs, if you’re concerned about hyperthyroidism in your own pet, we recommend offering a variety of protein sources so that your dog isn’t eating a steady diet of foods that could contain active thyroid tissue.

We also recommend taking your dog in for regular wellness visits with your veterinarian, at which time his or her blood thyroid hormone levels can be checked.

Hyperthyroidism is typically a condition seen in older cats. It is very rare in dogs, but three recent studies linking the condition in dogs to certain aspects of their raw diets are worth noting for all of you who also feed raw.

In most cases of canine hyperthyroidism, the cause is an aggressive thyroid tumor that over-produces thyroid hormone. The only other recognized cause is the ingestion of thyroid hormone from other sources, which seems to be what occurred in the recently studied dogs.

milupa profile image
milupa in reply to diogenes

Thank you for all the info!

At last someone mentions the clinical signs, which mostly apply in this sitution.

In the last chapter it mentions that ‘the only other recognized cause is the ingestion of thyroid hormone from other sources’ -that’s why I wondered if he might get my excess from my skin. I swapped HC cream to tablets for that reason.

efore the dog became allergic to beef I asked the raw feed supplier about the thyroid gland - he laughed and said that grassfed, organic beef thyroid glands were much too valuable to leave in the dog food, he sold them to a pharma company. Nevertheless I am vigilant about not feeding the cuts you mention.

Again, thank you for your help.

SeasideSusie profile image


Google 'hyperthyroidism in dogs' then print off some evidence to show your vet.

milupa profile image
milupa in reply to SeasideSusie

Hello SeaSideSusie - I read most of the answers and advice you give here and have learned a lot doing so. Thank You!

When I google as you suggest the algorhythm seems to change hyper to hypo or something like it, I simply cannot find anything usedul. I’ll keep trying!

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