Diagnosing Figlet - An Overview of Hyperthyroidism in Guinea Pigs
Thu Feb 4 09:37:27 UTC 2010
"Hyperthyroidism is a condition in which the thyroid gland is overactive, and makes too much thyroid hormone (called thyroxine and triiodothyronine). Hormones are substances that affect and control many important functions in the body."
While many animals have significant differences from humans and each other, many aspects of hyperthyroidism are the same across species. In guinea pigs (Cavia porcellus), this condition is thought to be extremely rare. Recent anecdotal evidence suggests that it may be more common than many veterinarians previously believed. Hyperthyroidism can cause serious problems with other parts of the body such as the heart, kidney and lungs. When diagnosing guinea pigs, problems in these organs are not always thought to be systemic. Given poor breeding habits and the fragile guinea pig body, when a kidney or lungs develop serious issues, there is often little hope for the animal. Doing further investigation to determine why the organs are failing is rarely done for a variety of reasons, primarily the perception of guinea pigs as 'just rodents' and the high cost of medical procedures on an animal that is likely near death.
I recently lost a guinea pig, Figlet, to hyperthyroidism, but learned a lot about it during the process. Because it is often difficult to obtain a definitive diagnosis, and because of the lack of information available on the condition as found in guinea pigs, I am publishing my observations and the case history of Figlet. This article is targeted toward guinea pig owners, but will contain a good deal of technical information that will be of interest to veterinarians. I am in a relatively unique position to write this article. First, confirmed diagnosis of hyperthyroidism is very rare in guinea pigs, as was the case for Figlet. Second, I happen to live in the same state as one of the very few doctors who have specifically studied this condition in guinea pigs. Third, I have a strong desire to help educate other guinea pig owners as they often care deeply for their animals, but suffer with the rest of us due to a lack of in-depth knowledge about guinea pig health.
Guinea pigs who develop hyperthyroidism may exhibit several symptoms that help diagnose this condition. These symptoms are not specific to the condition and may manifest to varying degrees or not at all. If you have a guinea pig that exhibits many of these systems, consult your veterinarian. These are described in more detail, as pertained to Figlet later:
* Excessive and frequent urination -- Often difficult to observe, especially in a multi-pig cage.
* Enlarged thyroid nodules -- Early development may be impossible to detect. Advanced cases may be as large as a pea and easily felt during palpation by owner or vet.
* Excessive energy / very active -- May seem to sleep less, run around more, exhibit more energy in or out of cage.
* Increased appetite and thirst for water -- May be difficult to observe in a multi-pig cage.
* Weight loss -- Even if eating more than usual, an observed steady weight loss.
* Higher temperature and/or heat intolerance -- Guinea pig may seek cool surfaces, avoid warm fleece and be warmer to touch than other pigs.
If your guinea pig exhibits these symptoms, consult a veterinarian. Be warned, many vets do not specialize in "exotics" (the term used by vets to describe most rodents, reptiles and birds). They will likely have no experience with hyperthyroidism in guinea pigs and will rely on their knowledge of the condition as pertains to cats. There is only a single test (nuclear scintigraphy) that can definitively diagnose the condition in guinea pigs, and it may be costly or not available from most vets. Blood work can only give an 'indication' and palpation of the thyroid gland may not reveal the mass until the condition has progressed. If left untreated, hyperthyroidism can lead to serious problems in the heart, kidney, lungs, spleen and possibly other organs. Surgery to remove the mass is possible, but very expensive and rarely performed.
I can either set you up with an account in the Records forum so you can move the information and update the article as you desire or move the current info there as it stands. You would be able to update this thread any time you cared to.
I will be moving it to the medical forum maybe at the end of the day.
I am in UK, I had a sow diagnosed through blood test with hyperthyroid. Other symptoms she exhibited, in addition with two or three of the ones mentioned above, were:
* Distended abdomen - despite the weight loss, she still had a very rounded "pot belly"
* Bulging eyes - not due to any problem in that area, she always came across as very "bug eyed". I later learned that this can be a symptom of hyperthyroid in multiple species - in my experience that includes guineas.
She was treated with medication for a few months, with Neo-Mercazole (carbimazole). However, due to age (est. 6 yrs) and the fact that she had clearly remained undiagnosed for a long time, I believe her body was weakened by the effects of hyperthyroid and when afflicted with a mobility problem, it was too much and she passed away very peacefully in her sleep.
Do you recall the bloodwork details, or can you get them? Aside from a *very* high ALT value, there is apparently no way to use bloodwork to definitively diagnose hyperthyroidism; it may be useful to diagnose other issues with thyroid levels. At least, that is what I was told by Dr. Johnston. If you had a confirmed case, sharing the bloodwork with Dr. Johnston would likely be very helpful.
Thanks for the note and input!
You mention ALT -- is that the same as the T-4 blood test? I thought that was a pretty good way to diagnose hyperthyroid, with the main problem being that normal values sometimes differ among sources, and some labs don't know how to do the test right. But there are some T-4 values that are definitely "high" as to indicate a thryoid problem.
I also learned that the nuclear scan was an option (we didn't do it) and that it's the only way to diagnose certain types of hyperthyroid where the thyroid itself is not the location of problem.
Also, just wondering: At any point was your piggy given tapazole? We believe the med slowed my piggy's weight loss and kept her alive several months; others have had some success with it as well. And, based on info about cats with hyperthyroid, my understanding is that it's a good idea to have an animal on tapazole a while before attempting surgery to remove the tumor (so body doesn't "freak out" from such a drastic change).
Just want to add those bits to the thread to possibly help others. Also, my vet (or her hospital) is now involved in a study where they're trying the radioactive iodine treatments (used on cats) on piggies (not many subjects/patients so far). If enough success, that may be another option in addition to tapazole or surgery.
I think probably there's a thread in the Medical Forum about my piggy, Inca, though not a complete case history full of dates and data. She was not super active, no bulgy eyes, and didn't drink more than normal. She very subtly lost weight at first, but continued to lose despite my efforts to compensate and despite a healthy appetite -- and when my vet felt a lump in her neck, we presumed hyperthyroid. She also had a fast heart, which is commonly secondary to hyperthryoidism. T-4 tests, unfortunately, didn't confirm the diagnosis. Nonetheless, we had her on tapazole and adjusted the dose a few times. It got to a point where she really didn't want the medicine anymore and became irritable toward me and her cagemates. It also didn't seem to be helping (continued weight loss). So I tapered off the medicine and eventually stopped, choosing quality of life over quantity; in hindsight the medicine was, in fact, helping her. She ended up dying from the aftermath of a thyroid storm, and partial necropsy confirmed a very large, bonelike tumor on her thyroid (we knew the lump was getting bigger). She died at half her peak body weight.
I'm not sure the best place for a compilation of thyroid experiences, but figured I'd add to this one.
pigdad347, I copied your post here to the Records forum and added a link to a copy of your complete page (all with links to your original page). Hopefully this will help others with similar problems.
Your case study:
I am not sure about the T-4. ALT is an enzyme in the liver they look at, I thought it was part of a standard blood workup.
Figlet was never given tapazole, no.
Regarding the study, it sounds a lot like what Dr. Johnston will be doing for upcoming research. His goal I believe, is to better understand bloodwork as it relates to hyperthyroidism, so it will start with testing on healthy piggies. Could you share your vet's name with me in private, so I can pass it on to Johnston?
Sorry to hear about Inca =( Did they by chance biopsy the mass? Curious if it was malignant.
For compliation of thyroid experience, this forum has already shown that it appears to be more prevalent than everyone thought (involved with Figlet). I really hope that some of these doctors that have experience with the condition could open some channel of communication. It sounds like together, they could likely make some pretty big leaps in diagnosing and possibly finding other treatments.
Thanks for the info!
pigdad, it's been a while since I was immersed in thyroid knowledge and lingo, but the T-4 test (I believe) is a blood test that checks the levels of thyroid hormones (though I forgot the names of them). I think some other (regular?) blood tests check liver values, though I'm not sure how thyroid activity is reflected in the liver. And I know checking kidney values becomes very important during hyperthyroid treatments; that's also a different blood test than the T-4.
I will send you my vet's info, and I was planning on giving her your vet's info, too (or directing her to read your case study). sounds like your vet is trying to learn more about blood tests to diagnose the problem, whereas my vet's study is involved in possibly treating piggies with a treatment that's been successful in cats. Most Internet searches about cat hyperthyroid will explain 3 courses of treatment: medical (tapazole), surgical (remove the mass), and radioactive iodine therapy (not available everywhere, but a good alternative for cats where the other two are not great options). The third has not been documented in piggies.
Yes, Inca's mass was analyzed post-mortem. I'd need to dig up the lab's report to re-read, but what I wrote in her thread was "thyroid follicular adenoma with osseus metaplasia" -- that's a benign mass with mineralization so that it was almost bone-like, which explains why we couldn't really aspirate from it.
I do hope vets learn more about this problem in piggies, esp. since it seems more common than everyone thinks. My vet also told me she was at some conference (after Inca's death, so within past 10 months; I think maybe August 2009) that had a session about guinea pig hyperthyroidism, where exotic vets agreed that T-4 tests/values need to be understood more broadly/consistently across the field (bad info circulating, even among vets). She was also surprised that thyroid surgery is being done/recommended without the hesitancy that she feels (based on consulting with a top endocrinologist for cats) and without giving tapazole for a while prior to the surgery. Very few surgeries have been successful long-term, I believe.
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There are also a few notes in this thread; quick summary of Scooby's case:
My 6 year old pig Scooby was hyperthyroid. She was losing weight although we were feeding her 70 grams of Critical Care a day. Her vet had trouble getting reliable T3 and T4 levels, but we ruled out everything else and used the standards for treating hyperthyroid cats. Scooby responded to methimazole. which works very slowly. We increased her dose very slowly over a period of months until her weight stabilized. Then she was OK for about 9 months, although her T3 and T4 levels were still high. I'm sorry I do not have the numbers.
Scooby's final medical crisis was a "thyroid storm", which may be happening to your friend's cavy. The thyroid rapidly releases so much hormone that her temperature and heart rate shot up. Again, the vet used the protocol for treating cats when this happens (different medications from methimazole). Scooby did respond to this treatment. Although we put her down--she probably had a thyroid tumor--it appears that the well-understood standard treatment for cats does work in cavies as well.
In the meantime, I found a web page that we laypeople probably should not have access to (since it says "members only"): http://www.aemv.org/members_only/proceedings.cfm PDF downloads are available that summarize sessions at the 2009 AEMV conference (Association of Exotic Mammal Veterinarians), including a couple about hyperthyroid in guinea pigs.
pigdad, since your vet has an interest in the topic, he/she may want to contact the authors/presenters listed... though perhaps he/she was at the conference to hear the info first-hand!
I'm also going to post this link on my Inca's thread, but I'll leave it up to GL "powers that be" to add the link elsewhere -- maybe the T4 thread is another good place.