Hypothyroidism (ii thyroid hormone depletion) can be missed, even by veterinarians. An underactive thyroid gland is common but visible symptoms of a thyroid problem (poor coat-skin, overweight, "lazy") are often overlooked.
THYROID DIAGNOSIS & TREATMENT
A Keeshond breeder in Georgia had a 23-pound (10kg) dog that, in late middle age, reacted to its hypothyroidism with what the owner described as “paralysis” and the vet called “hypothyroid neuropathy”. Neither of them had previously seen this, although I have several similar pieces of correspondence from other owners who have had similar experience. When they finally thought of the possibility of hypothyroidism and confirmed it, the dog Rikki was started on tablets of Soloxine at 0.1mg BID (a total of 0.2mg per day).
Typical of other owners, she called the symptoms “scary” and the recovery, once medication was started, as “miraculous.” The Kees never had a relapse of the paralysis (I followed up when she was elderly), not other symptoms, and the thyroid function, checked every 6 months, remained in the safe normal range.
A correspondent in the UK told me she is treating her second hypothyroid Chow-Chow, eleven years old and 35 lbs at the time of this writing, and it has been on the medicine for four years as of this writing. In her country she is using “Forthyron-400” (had used Soloxine on the previous Chow). Her story is typical of many whose vets do not recognize the symptoms as indicative of thyroid dysfunction. Here is part of what she wrote to me:
“Heaven [the first bitch] when started on the treatment was at death’s door -- she was severely hypothermic (we couldn't get a reading on the thermometer), totally uncoordinated, her eyes were ulcerated, and still the vet was diagnosing HD and entropion. I insisted she do a full set of thyroid tests – previously, when I asked her to test, she only did a simple blood test. But by the time we tested for thyroid this next time, it was almost impossible to get blood from her. Her weight had dropped to next to nothing but her head was quite puffy. The change, once medicated was amazing. We only managed to get one test, as it was so hard to take blood. Even using a needle as big as those used to insert chips, it still clogged up as soon as the blood was being drawn up the shaft.”
Speaking of this vet and her current dog, the lady said, “I think she should always test [for hypothyroidism] when there is a change in behavior (lethargy, grumpiness) and the brittle coat with bald areas. [This] is a pretty good indication, and we have discussed this on more than one occasion.” The dog in question is related to “Heaven” — this second one’s maternal grandsire was the first bitch’s sire. Both developed severe signs well after mid-life, which follows a general pattern in my experience. I have noticed that by the time symptoms are obvious, the affected dog is usually between four and ten years of age, more often middle-aged than geriatric.
In the UK and in vet circles elsewhere, the synthetic product is chemically identical to the naturally occurring T4 is referred to as levothyroxine sodium, the active soluble isomer of thyroxine. The likely reason for the vet’s confusion (other than inexperience or perhaps absence from the classroom when the lectures on hypothyroidism were delivered) was a plethora of symptoms due to the fact that basal cellular metabolism and oxygen consumption changes affecting the function of virtually all organ systems can be confusing. Especially by the time the condition has worsened without proper treatment. The dog owner must take it upon himself to “bone up” on health matters and ask specific and leading questions.
On that site, the recommended starting dosage and frequency is 10 micrograms per kilogram of body weight orally every 12 hours. A kg is 2.2 pounds, so this equates to 0.1 mg (milligrams) per 2.2 lbs. of dog, or approximately 3 mg for a 66-lb. dog instead of the 0.6 to 0.7mg tablets of Soloxine that most U.S. vets would start with. Four to five times the typical American dosage. Because of variability in absorption and metabolism, the dosage may require alterations before a complete clinical response is observed, and these represent merely a starting point. Clinical results will determine how you and your vet tweak the amounts, probably even better than plasma T4 levels retested two weeks after dosage changes could, and it could take four to eight weeks to see it in the dog’s coat, behavior, etc. Once you get satisfactory results, clinical and biochemical monitoring can be performed less often, such as every 6 months or annually. Every dog is a little different, so take your lead from the patient.
CHEMICAL vs NATURAL THYROID GLAND SUPPLEMENTS:
Adverse effects of thyroid hormone therapy are rare and generally associated with excessive dosage, but as I mentioned, you can vary this a lot without danger. In at least one experiment, overdoses of three to six times the label-recommended starting dose for four consecutive weeks resulted in no significant clinical signs that could be attributed to treatment, which is why I refer to Soloxine as “safe”. However, chronic overdose can eventually lead to problems. Many affected dogs are on other medications, so you need to do your homework such as studying that CEVA site I referenced. One common drug perhaps too-widely prescribed is prednisone, which increases T4 binding to serum carrier proteins, so this may result in lower T4 transfer rates from serum to cellular sites where it is needed. More likely than overdosing, you may need to increase dosage if symptoms remain or return.
The following paragraph or two perhaps could be in the above section on treatments and testimonials, but I also feel the subject should be segregated. Some “alternative”, “naturopath”, or “holistic” writers, with variable levels of scientific training, understanding, credibility and qualifications, have suggested dietary preventive measures such as adding a bit of iodine-rich kelp to canine food rations, or avoiding soy (claiming it has thyroid depressant action) and not using “chemicals” to fight parasites... such latter statements really irk me, since as a chemist I decry the abysmally poor education the nation’s children have had for so many generations, under teachers who don’t seem to know that everything is composed of chemicals. These current “manglers of meaning and desecrators of definitions” usually are not careful enough to explain that what they should be complaining about is the overload of synthetic or harmful substances, an “unnatural” excess. Extremism, as Barry Goldwater said, is no vice in the defense of liberty, but it might be in the field of health.
On the other hand, there may be some “alternative” treatments that are beneficial. If you are willing to take the risk with your dog, you can investigate these. Elemental iodine compounded with potassium iodide (5 mg I with 7.5 mg KI per tablet) in a product called Iodoral or Lugol’s solution, made by Optimox, is one example, though I hesitate to mention it simply because I have no personal experience or close knowledge of its efficacy. I know Soloxine works, and though I’d prefer to get any medicines without prescriptions, I feel a little more confident going with what I know. The Iodoral has been promoted for treatment of corals in salt water aquariums, and a number of other things that make sense because of the antimicrobial (killing) effect of active iodine on a variety of fungi, bacteria, etc. But whether the Optimox iodine is actually taken up by the thyroid and used there to “repair/rejuvenate” the gland has not yet been proven to my satisfaction. I want to see double-blind control study results before giving much credibility to such reports.
Potassium iodide (KI) by itself, without the more toxic elemental iodine, is generally preferred by the medical profession for the purpose of adding dietary or medicinal iodine to the body via the gut and/or circulatory system. Elemental iodine is toxic in normally significant amounts (which is why it has been used as a disinfectant). The main reason the potassium iodide is in the formulation is probably because elemental iodine by itself is not water-soluble, but in this Lugol’s ratio, it is made so. The solution was at one time used in the treatment of gout and as a first-line treatment for iodine-deficiency hypothyroidism in adult humans. It has been used in a variety of “alternative medical” treatments for several health problems, and until 2007 was an unregulated over-the-counter product in the USA, sold as a general reagent, antiseptic, preservative, emergency disinfection of drinking water, or medicine for human or veterinary application. As of mid-2007, however, the DEA (Federal Drug Enforcement Agency) now regulates all solutions containing more than 2.2% iodine because they potentially may be used to make methamphetamine. However, as of this writing, you can still get up to one fluid ounce (30 ml) of Lugol’s exempt from this regulation in the USA. It is currently available over-the-counter in Canada and Mexico without such restrictions.
One must be very careful with dosages. Sometimes a tremendous excess can have the exact opposite effect from what the amateur administrator intended. Examples might include vitaminosis with A and D, overloading with calcium supplements that have the effect of shutting down the assimilation of that mineral, etc. If you “overdose” a dog with iodine, you could even cause the Wolff-Chaikoff effect, which is a hypothyroidism caused by ingestion of a large amount and consequent elevated levels of circulating iodide. It is referred to as autoregulatory phenomenon and inhibits formation of thyroid hormones which, of course, is opposite of what you most likely are hoping to accomplish. High levels of intracellular iodide suppress some thyroid enzymes, and reduce synthesis of thyroxin. Wolff-Chaikoff effect can be used intentionally to shut down an overactive thyroid gland, but generally in 10 days it wears off.
POSSIBLE THYROID EFFECTS on OTHER DISORDERS:
What about the seemingly wild claims about benefits of thyroid therapy on “other” health problems? Does Soloxine (etc.) hormone replacement/supplement truly have beneficial effects elsewhere, i.e., in connection with other disorders? Probably in many, perhaps in others. Search Pubmed for a case report of megaesophagus successfully resolved after thyroid supplementation.
Robert Washabau, a diplomat in internal medicine on the faculty of the U. Penn vet school, is quoted as saying, “Routine hematology, serum biochemistry, and urinalysis should be performed in all cases to investigate possible secondary causes of megaesophagus (e.g., hypothyroidism, hypoadrenocorticism). …additional diagnostic tests… thyroid function test... dogs affected with hypothyroidism should be treated with levothyroxine.” Curiously, the same man hedged a little when as a co-author of another study, they did not sound as positive, saying, “this study did not reveal a clear association between hypothyroidism and acquired megaesophagus.” J Am Vet Med Assoc. 1997 Dec 1;211(11):1406-12. Risk factors for acquired megaesophagus in dogs. Gaynor AR, Shofer FS, Washabau RJ. 1
Indeed, Wendy Brooks, DVM, is also at least as cautious in her article. 2 “Hypothyroidism may be associated with megaesophagus. It is easy to rule thyroid disease in or out with blood testing and it is important to treat a thyroid hormone deficiency; however, megaesophagus usually does not correct with thyroid replacement therapy. Whether or not hypothyroidism can truly cause megaesophagus is still being debated.”
Washington State vet school, said, “Less commonly recognized signs that may be seen in a small number of dogs with hypothyroidism include dilation of the esophagus (megaesophagus) …and abnormal ability to walk.”
THYROID & NUTRITION:
A word about nutrition might be appropriate here. We know that dog food companies do a lot of blending, and geographic sources of ingredients would be impossible to report in an accurate and current manner. We also know that soil (and thus, grain and beef raised on it) varies considerably across the country in regard to such things as selenium content. Additionally, not all suppliers may be as convinced as some scientists about the need for a minimum amount of this mineral that is considered synergistic with vitamin E and other nutrients, so they may not adjust its level in their brands. Now, I fully realize that in 2008, an experimental program seemed to refute earlier claims of the benefits of vitamin E and selenium, but that study may have been flawed, and I still hold to other evidence that shows these are beneficial. The proponents of vitamin E and selenium supplementation (and I am one) will again have their day, I predict.
Here is the latest on that study: The National Cancer Institute, in 2008, cancelled a $120 million trial of 35,000 men taking selenium and vitamin E supplements as possible safeguards against prostate cancer. The trial ended four years into the projected 7-year period after scientists saw an unexpected increase in tumors among some of the men taking vitamin E, and a rise in adult-onset diabetes in some of those taking selenium. There could be other reasons for an apparent rise in incidence... one of many might be that some men taking such supplements have a false sense of security and reliance on the “miracle-vitamin”, and consequently do something stupid in some other diet or health-practice area, thinking they are invincible.
Such swings in opinion often are based on studies that are not all that well-designed in regard to eliminating other incidental causes for what results the investigators compile. For a recent example, cholesterol-lowering statin drugs were thought to yield better PSA tests in men, but lately it has been learned that they primarily reduce levels of a blood marker for prostate cancer, so it may be that they only mask the disease rather than actually lower the risk.
“Even mild selenium deficiency may contribute to the development and maintenance of autoimmune thyroid diseases” a statement that comes from PubMed.gov4, along with “In areas with severe selenium deficiency there is a higher incidence…” And, PubMed.gov 5 tells us, “Selenium deficiency produced up to a 14-fold decrease in hepatic T3 production from thyroxine (T4) in vitro.” Dr. Havashida’s study, Selenium Deficiency and Hypothyroidism.
It must be acknowledged that there is no selenium in the thyroxine medication, and no reported level in the thyroid gland. Whether there is a direct connection or simply a beneficial effect on the whole body, or no real need for selenium in specific application to thyroid deficiency, is something that I do not think has been studied. We know that selenium is beneficial, and that Soloxine is a near-miracle drug for sick thyroids, but is there synergism or any connection? I think so, but I cannot state that as a fact backed up with scientific studies.
Complicating the picture is the apparent condition in some areas where diets contain adequate iodine but are selenium-deficient. High or normal T4 analysis may give a false sense of security, because T4 blood levels have been seen to rise when there is selenium deficiency, perhaps as a defensive reaction by the body. However, when this happens, it is often accompanied by depressed levels of T3, which is characteristic of those low-selenium, normal iodine regions.
T3 is converted by the body into T4 as needed, but it is very difficult for the dog owner to administer that without getting into toxic doses. It is much safer to give T4 and let the dog convert it internally. A few dogs are unable to do this, and these may require frequent medical monitoring by your vet. Some few dogs are able to get back to normal metabolism and do away with the need for thyroxine, but don’t count on it. If you follow up every couple of months, and see if dosage needs to be changed, long-term therapy can be very satisfactory. The good news is that Soloxine is cheap compared to most medicines, and your vet clinic visits can be spaced out further and further apart if the first months give good results.
If we learn nothing else, we should come away from a study of the endocrine system with the realization that not only do all the glands have effects on the others, but that there are many analogous biochemical interactions that teach us that the well-functioning body is a marvel of balances. Vitamins, minerals, vaccines, hormones, nutrition, medicines, genes, exercise activity — all are important to a healthy life, and in moderation, for the most part. The definition of homeostasis is appropriate here: The maintenance of steady states (you can call that “health”) in an organism by coordinated physiologic processes. Thus all organ systems are integrated by automatic adjustments to keep within narrow limits disturbances excited by, or directly resulting from, changes in the organism or its environments.
Sometimes, to restore or approach such homeostasis, we need to medicate. If you can accomplish it by careful breeding, all the better, but we live in an imperfect world, and sometimes we need a little help from our medical or chemical friends.