Revised 2012.
INTRODUCTION
Although I am mostly a German Shepherd Dog breeder, I have much all-breed experience in breeding, handling, judging, and consulting; as a scientist I also have been drawn to certain medical aspects of cynology (dog science). In this article, we will look primarily at the endocrine system. True endocrine glands are the pituitary, thyroid, parathyroids, and adrenals. A characteristic of endocrine tissue is the production of chemicals (called hormones) that affect other body systems such as other organs, glands, and nerves.
This said, we will table most of the discussion of the chemistry, and proceed to introduce the subject; viz., the fairly common occurrence of impaired health that is traceable to, or at least suspected of coming from, a defective hormone production and regulatory system—specifically involving the thyroid gland. Incidentally, some readers may already know that Greyhounds, GSDs, Chow-Chows, and other breeds have more incidence of low thyroid activity than the general or average dog population. Some breeds of dogs do better (have less “need” of equivalent levels of the hormones) than others, but enough breeds do not, especially in the low normal range. If your vet picks up a textbook that tells him your dog must be healthy because it is within that range of “low-normal,” sing to him or her from the Gershwin song, “It ain’t necessarily so!” Also, remember that the base ranges that are now considered the norm were established on such breeds as Beagles, and that breeds do indeed differ in regard to their hormone needs. The list of “exceptions to the rule” has grown so much that any reliance on the old “normal” range must now be considered foolish for that growing number of breeds. But just try to convince your vet of that, when he has not been doing original research in this field.
All endocrine glands are “connected”—i.e., they can influence each other’s action and efficiency. If any part of the endocrine system is out if kilter, so will be the rest. If the endocrine system is not running properly for any length of time, damage could become permanent (adrenal failure, pancreas failure, etc). Two of the most important glands in this discussion will be the pituitary and the thyroid. For a detailed discussion of the pituitary dwarfism in the GSD and related breeds, see www.siriusdog.com/articles/ or use a search engine [such as Google] to find my articles elsewhere on the Internet. Additionally, you can order my book on the GSD. I recommend you get the Orthopedics book at the same time. See the note at the bottom of this article.
Additionally, function in a couple of the endocrine glands can be mitigated or influenced directly by environment. So, it’s a tricky thing to adjust all these factors and treat your affected dog. Since we are discussing the thyroid in this particular article, let’s start with what it is and what it’s supposed to do, before getting into what to try to fix your problem.
In an excellent treatise on the subject some years ago, John Cargill reported: “In the dog, the thyroid gland consists of two lobes flanking the trachea (windpipe). It has been established that it secretes at least two related hormones, T4 (thyroxin) and T3. Even though the thyroid gland secretes mostly T4 (about 90%), it is T3 that is considered the active form of the hormone.”
These two principal thyroid hormones are derivatives of an amino acid called tyrosine. You’ll remember from High School Biology that amino acids are the building blocks of proteins, which in turn are the main components of many body tissues such as blood, muscle, ligaments, and more. If there is a need, the normal pituitary gland signals the thyroid gland to send out TSH (Thyroid Stimulating Hormone); the thyroid then produces more T4, some of which is converted into T3. Measuring just the T4 levels to diagnose hypothyroidism is ineffective. In the UK and in vet circles elsewhere, the synthetic product chemically identical to the naturally occurring T4 is referred to as levothyroxine sodium, the active soluble isomer of thyroxine.
The Thyroids and Their Hormones — Although these glands aren’t very often frankly (obviously) defective, when they do malfunction, the result can be hair loss (in about a third of the cases), overweight (half), physical lethargy and/or mental sluggishness (a third), behavioral changes (far fewer), and other problems. Since these symptoms can be attributed to other disorders, you could have a blood test run before jumping into treatment if you have any doubt. Although most common in Goldens and Dobes between 2 and 6 years old, gradual decrease in thyroid function is to be expected in aging dogs of many breeds, and can result in a loss of fertility, poor coat, puffy belly, wrinkling skin, muscle weakness, and lowered appetite and metabolism. Fleabite allergic reaction can either mimic or perhaps even act as a stimulus to onset of low grade hypothyroidism, but administering TSH (thyroid stimulating hormone) in conjunction with the more accurate free T4 tests can be helpful in diagnosis of the more severe cases.
To an organic chemist such as I am (or was, since I’m retired now), the two principal thyroid hormones are seen as derivatives of an amino acid called tyrosine, containing iodine in the form of iodide ions (charged atoms). These hormones are thyroxine (also designated T4), and triiodotyronine (T3), those numbers referring to how many iodide ions are attached to each molecule. The hormone molecules consist of two tyrosine structures linked together, with iodine “stuck on” at three or four positions.
The gland secretes much more T4, but T3 is considerably more active. In other organs of the dog’s body, especially the liver and kidney, T4 is converted to T3 by stripping off one iodide ion from each molecule. T3 is quite potent, and since the healthy body makes its own in those organs, it is unwise for most people to ask that T3 supplementation be attempted. T4 is quite safe in almost any reasonable amount. Along with transthyrein and albumin, a globulin type of glycoprotein synthesized in the liver transports both through the body via the circulatory system, to where the molecules are needed by “target cells.”
One breeder-researcher-writer I corresponded with came up with an interesting analogy. He said, “T3 is the work-horse hormone. If there is a need, the pituitary gland signals the thyroid gland to send out TSH; the thyroid then produces T4, which in turn is converted into T3 and other thyroid hormones. T4 is the gas at the gas station, and the T3 is putting that gas to work. This is why simply measuring the T4 levels in a dog to diagnose hypothyroidism is not correct.”
In Vet School, a student may not get as much useful data as circulates among experienced breeders. This is the case in many areas, such as breeding and reproduction, nutrition, and breed-specific health issues. For example, most vets are taught (and repeat) that young dogs don’t have thyroid hormone deficiencies, so they don’t test for this unless the owner insists. In almost every case, the results will indicate that (according to their textbooks and inadequate practical experience) there supposedly is no problem with thyroid hormone levels. You don’t have to agree with this conclusion, though. Once in a great while, the disorder might progress far enough to affect the T4, T3, and other indicators enough so that the suspicions of the owner are confirmed, and the surprised vet’s eyebrows are raised twice: once at the test results and again at the remarkable recovery that often occurs in these patients after Soloxine or other thyroid “medicine” is administered. Even some of the most experienced are often surprised when other problems go away. For example, “fixing the thyroid usually fixes the adrenals,” as a vet friend once told me. In my experience, it fixes a whole lot more! But if you can’t persuade your vet to experiment instead of continuing to trust in what I consider poor science, you are out of luck, and you and your dog may continue to suffer.
SYMPTOMS OF THYROID INSUFFICIENCY OR OTHER MALFUNCTION
Although we customarily speak of them in the singular sense, the thyroid glands are paired structures located along the windpipe (trachea), about one halfway down the neck of dogs. This gland has a number of functions, but the important ones can be revealed and one sees what can happen when it does not work properly: loss of haircoat (alopecia), weight gain and edema, poor heat-stress tolerance, increased dandruff, itching to the point of self-mutilation, smelly crud build-up in the ear canals, rancid body odor (especially in mature dogs), decreased fertility, lethargy, poor digestion and stool condition, possible fever, darkened or less-supple skin, lowered resistance to flea infestation, or any combination of these. Insufficient hormone levels can give almost unnoticeable signs, but the experienced dog owner might pick up on them before the problem gets really bad. And a change in the environment, such as greater exposure to fleas, might shift symptoms into the frank (obvious) category. By this time, when the vet admits your dog has a problem, it will be much more difficult to deal with it.
Of course, some of these symptoms can be caused by other things, as well. For example, if alopecia is not caused by direct thyroid malfunction, it might be from disease such from parasites; intestinal worms and other foreign invaders can cause malnutrition by blocking the body’s normal uptake of amino acids needed to produce protein for replacement of hair and other cells lost naturally (they do die off) or from disease, however mild.
Other signs, though less common and certainly also attributable to different disorders, might include neurological symptoms such as behavioral changes (including, at worst, unprovoked aggression), head tilting, circling such as in tail chasing or appearing to search for a good spot to lie down in but never getting there), what appears to be seizures, ataxia, and lack of control of facial muscles. Remember, these are the extremes, and in most dogs you will find only the hair loss, ear crud, and one or two other indications. Abnormal behavior in dogs can also have a variety of medical causes, but one of them might be sub-optimal thyroid function. However, behavior is very complex because it not only reflects the functioning of the whole physical and psychological organism, but it changes as a result of environmental influences.
Keep in mind that the various parts and systems of the body are all inter-related, that a disruption in the process of one may have its origin or an effect in another. The endocrine system is a prime example, with hormones being produced in more than one gland and greatly influencing some or all of the other glands. An example that, in my opinion, has not yet been thoroughly explored is the very common set of problems GSDs have with yeast/fungal infections, flea saliva allergens, and general autoimmune system weakness. I have observed countless cases of dogs with a combination of seborrhea, low resistance to fleas, nagging ear infections, interdigital pyoderma, and other “complaints.” The lines between these dots and their relation to thyroid insufficiency, I feel, will someday be drawn with more clarity. But the dog owner and the vet should not rule out “subclinical” hypothyroidism.
MORE ABOUT SYMPTOMS AND ALLIED PROBLEMS
Thyroid-imbalance/hypothyroidism signs commonly include: flea-saliva allergy, hard & cracked pads problems, problems with the outer ears (such as leathery, swollen, dark, smelly, or cracked skin lining the insides of the ear shells and a leathery, semi-bald texture to their outer sides). Cystic ovaries or irregularity (or absence) of estrus, are sometimes associated with these other signs. Rear limb lameness is often associated with thyroid insufficiency, but it is anyone’s guess as to being coincidental or linked. These symptoms could point to general endocrine and immunological failure, but more often than some people want to admit, thyroid disorder is at the core.
Fungus — Sometimes a chronic swelling and uncleanness of the external ear canal is blamed on mites, when the immediate cause may be a fungus. Whether picked up from straw bedding or simply the air currents, the fungus attack is often fought on two fronts: dogs with this infection in their ears will also frequently have a fungal redness between their toes. In addition, the irritation, scratching, and licking/biting that the dog engages in can open the way to bacterial infection which can easily be combated with neomycin sulfate (Panalog, etc.). The fungus, however, must be treated with a fungicide from your veterinarian, and there are preparations that contain both it and an antibiotic. This is a good idea, because treating only with an antibiotic favors the more rapid growth of fungi, presumably because it kills certain bacteria that are inimical to fungus. Additionally, these same symptoms may result from thyroid function insufficiency of a genetic or acquired nature. It can be difficult to distinguish between primary and secondary (stemming from other causes) hypothyroidism. Have your veterinarian check thyroid hormone levels and treat dog and premises for fleas, because dogs with poor general immune response are at higher risk for fungal infections as well as for other ailments.
Seborrhea — This is a term applied to a condition in which there are scaly patches and a greasy feel to the dog’s skin. You might notice great difficulty in keeping the ears clean and free of dark wax and yeast or fungus. Often, the dog will have a rancid odor. Many of these cases are related to thyroid hormone imbalance, and such an immune- and general endocrine-related disturbance may become chronic and in need of very frequent cleaning with little or no hope of remission. Seborrhea, however, can be caused by a number of things, so ask your veterinary dermatologist to try to find the underlying cause as well as give you ideas on how to treat for the symptoms. I have seen a large number of cases where prolonged exposure to (and poor defense against) fleas have apparently weakened a dog’s immune response and thyroid function, resulting in severe seborrhea. Old dogs are especially vulnerable to this regression, probably because of lowered efficiency of thyroxine production. Hair loss is common. If the dog shows evidence of much itching, it is usually called secondary seborrhea, which refers to a primary cause being marginal thyroid insufficiency, mange, fleabite allergy, or other trigger influences, involves relatively large reddish-skin patches with hair loss, and is often more scaly and less greasy than is the primary form. Primary seborrhea is something GSDs seem to be more predisposed to than are most other breeds, and it is this type that more affects the ear and an increase of bacterial colonies on the skin. It is a chronic condition that requires constant or renewed treatment regimens with no hope of eventual cure, just some control.
A Quick Word about the Endocrine System — True endocrine glands are the pituitary, thyroid, parathyroids, and adrenals. A characteristic of endocrine tissue is the production of chemicals (hormones) that affect other body systems such as glands, organs, and nerves. Keep in mind the fact that all the endocrine glands have varying effects on the others.
Von Willebrand’s Disease — There obviously is no “cure,” but for those very few dogs that suffer from both vWD and hypothyroidism, the use of the thyroid hormone medication seems to alleviate vWD symptoms also, to some extent. It might be worth experimenting with TSH, thyroxine, and other such approaches under your veterinarian’s supervision (if you can twist his/her arm), to see if vWD by itself will be affected. The reason not much progress has been made in eradicating this disease in the USA is two-fold: too many uninformed or incompetent people are breeding dogs, and the GSD Club of America has so far shown a lack of initiative. Probably 20 percent of Shepherds, perhaps higher in some linebred families, have vWD, and since it is detectable through blood analysis, there’s no excuse for ignoring the problem.
Pituitary dwarfism — This disorder of little-known inheritance mode is somewhat rare, but obviously present in the breed. I believe it is the result of recessive genes acting in the homozygous state. Since the pituitary directs the functions of other glands as well as regulates growth, the dogs with this disease are not only arrested early in size, but of precarious health unless treated with hormones. Most of the poor health may be a result of reduced thyroid activity, so dosing with thyroxine can help a dwarf live a fairly normal life. It also allows them to grow a normal haircoat.
TREATMENTS
Dr. Jean Dodds found that treatment for frank (obvious, clinical, unquestioned) thyroiditis, along with a one-month tapering-off course of low-dose corticosteroids, successfully reversed many behavioral problems such as aggression, extreme shyness or seizure-like activity within 10 days to eight weeks. Her team found out that thyroxine treatment is a good approach even without the corticosteroid. She has not gone as deeply into the effects of selenium on thyroid hormone production as others, but has made cogent observations on the connection between thyroid function and several aberrations such as behavior changes at puberty, allergies, skin problems, reaction to parasites such as fleas.
While I’m on the subject of that pioneering vaccine scientist, I want to insert a note here: despite a report in J Vet Intern Med 2006;20 suggesting no relation between thyroid problems and vaccines, I believe the overuse of vaccines in susceptible individuals does indeed adversely affect the overall immune system, and the thyroids in particular. Dodds is well-known for exposing myths that have long fostered excessive and unwarranted vaccine use.
For many years I have practiced limited vaccination schedules (now proven by scientific studies to be wiser than the old frequencies), especially with old dogs. I have also seen hypothyroidism appear or worsen after or concurrently with a failure to control fleas and a resultant flea-bite allergy (flea saliva contains antigens). However, this observation may well be, in most cases, a result of a dog with poor thyroid function being more prone to flea-allergy reaction.
I am certainly not defining my “good luck” beyond careful choice of breeding stock, but for many years I have practiced what I considered common sense: limited vaccination schedules, especially with old dogs, living in low-pollution areas, and a refusal to nearly drown dogs in every drug that the industry or vets wanted to push. I have seen much evidence of a genetic foundation for hypothyroidism (or at least the “weakness” or propensity to develop it), but I have also seen hypothyroidism appear or worsen after a failure to control fleas and the resultant flea-bite allergy (flea saliva contains antigens). The reverse is also apparently true: a dog with poor thyroid function will likely be prone to flea reaction, and a dog that has been subjected to long and overwhelming burden of contact with fleas might have its thyroids “damaged” as a result.
A recipe for health that has held up well for me for many decades of breeding has been: a well-tested & well-balanced nutrition/diet, moderation in medicine, plenty of exercise and fresh air, indoor humidifiers in winter, and watchful parasite control. Others can feed all the raw chicken, yucca, and pixie dust they want, but so far, they have not come up with any good, logical, scientific refutation for my success as a dog owner since 1937 and breeder since 1945. They can’t effectively argue with results. Nor will either camp likely convert the other. In all the hundreds of pups we’ve produced and the numerous dogs that lived their lifespans with us, I only had one that suffered from hypothyroidism and had need for regular flea control for a while and ear cleaning for a longer period. She had been sent off to travel and compete in the “care” of another professional handler (my mistake… I was too busy handling clients’ dogs to campaign her myself!) When she returned, she was in terrible condition, with the flea and thyroid condition plus a mummified puppy that was retained (she had been bred and delivered while in his hands). I bring up this incident to illustrate the complicated interaction of genetic and environmental factors in the appearance and severity of thyroid-related disorders.
In my successive roles as breeder, handler, judge, and writer, I have been witness to much that deals with this subject, so I do not have to rely on my own luck or lines for my data. One of the lessons I have learned is that there is a range of treatment results from barely perceptible to nearly miraculous. The treatment I refer people to is the use of synthetic thyroxine. Soloxine® is one brand name; another is Synthroid®. You may also come across the Thyro-Tabs® brand, or Armour® Thyroid Tablets sold for human consumption. The website www.armourthyroid.com has lots of very good information, including effects on reproduction. Other informative websites include (if these are still current) www.thyroid.about.com/ and www.soloxine.com/. Whichever you choose, you’ll have to get a prescription from the vet, if you live in the USA.
I have seen amazing results with Soloxine in a number of health needs, especially in fleabite allergy cases and in fertility of bitches that have previously failed to conceive. Many times this temporary sterility seems to be prevented by a couple weeks of administering Soloxine. Forget the T3 tests if you just want to boost conception or try it out for frank or even subclinical hypothyroidism or more other minor problems such as unexplained hair loss on chest, belly, and a few other places (after you’ve positively ruled out fleas). Just try to convince your vet to sell you a good-size bottle and let you experiment, with his/her occasional supervision. You might ask him/her to let you start with a dosage level of about 0.1 mg (milligrams) in divided doses, per ten pounds of body weight. In my experience and that of many vets I have discussed it with, Soloxine (or the other brands) is extremely safe; none of them were concerned about “overdosing.” One British website with dosage info is:
http://www.noahcompendium.co.uk/CEVA_Animal_Health_Ltd/Forthyron_400/-40032.html
but they suggest four to five times the typical dosage used by most Americans. Every dog is a little different, so take your lead from the patient. 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, in regard to interactions.
Typically, the daily dosage is divided, the tablet halves being given orally approximately 12 hours apart, though the exact timing is not important. Some of my correspondents report satisfactory results with once-a-day doses of 0.1mg per 10 pounds, while more claim or think they need to give that much two times a day. You can either experiment with this very safe product and determine for yourself what is enough, on the basis of visually observing results, or you can help pay for your vet’s Lexus by letting him run periodic blood tests for T3/T4 levels. Perhaps every month or two until you get an idea of ideal maintenance dosage. One reason for twice-daily medication is that about half of the hormone is used and excreted from the body within 12 hours. Another is that it helps control thyroiditis by shutting off TSH production in the pituitary, and “calming down” the dog’s thyroid follicular cells and thereby inhibiting production of the antithyroid antibodies that give rise to symptoms.
Typical Testimonials — 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.” Her Kees never had a relapse of the paralysis (I followed up when she was elderly), nor 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, having been on the medicine for four years as of the time she wrote to me. 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.”
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 behaviour (lethargy, grumpiness) and the brittle coat with bald areas. [This] second dog is related to ‘Heaven’—both developed severe signs well after mid-life.” That followed 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 vet circles, the synthetic product chemically identical to the naturally occurring T4 is often referred to as levothyroxine sodium, the active soluble isomer of thyroxine. Vets (especially those who are not actively breeding dogs) are frequently confused, so the dog owner must take it upon himself to “bone up” on health matters and ask specific and leading questions. For the UK readers of this article, see the following website:
http://www.noahcompendium.co.uk/CEVA_Animal_Health_Ltd/Forthyron_400/-40032.html On that site, the recommended starting dosage and frequency is 10 micrograms per kilogram of body weight orally every 12 hours. Four to five times the typical American dosage. 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. 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.
OTHER INFORMATION
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. I believe the wise protocol is to go up or down in amount until you find where your dog’s symptoms are under control.
Some “alternative,” “naturopath,” or “holistic” writers, with variable levels of scientific training, understanding, credibility and qualifications, have suggested other treatments, but I caution you to be both careful and skeptical. I want to see double-blind control study results before giving much credibility to such reports. 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.
POSSIBLE 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. For example,
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11680912> is a case report of megaesophagus successfully resolved after thyroid supplementation.
Allow me to refer you to some more studies:
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9394890&dopt=Abstract>,
<http://www.veterinarypartner.com/Content.plx?P=A&A=604&S=1&SourceID=42>,
and <http://www.vetmed.wsu.edu/ClientED/hypothroidism.asp>.
INTERACTION WITH OTHER NUTRIENTS
“Even mild selenium deficiency may contribute to the development and maintenance of autoimmune thyroid diseases” is a statement that comes from
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11932302&dopt=Abstract>, along with “In areas with severe selenium deficiency there is a higher incidence…” And, <http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3435458>
tells us, “Selenium deficiency produced up to a 14-fold decrease in hepatic T3 production from thyroxine (T4) in vitro.” In http://www.avianweb.com/hypothyroidism.htm>, we find Dr. Havashida’s study, Selenium Deficiency and Hypothyroidism. There are many more such works in the medical literature.
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 between these two, as there is between selenium and Vitamin E? 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.
Some affected dogs are able to get back to normal metabolism and do away with the need for thyroxine, but don’t count on it happening. If you follow up every couple of months or take note of appearance changes, 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. The bad news is the stubbornness of most vets in refusing to treat (they see it as a request to experiment).
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 any disturbances excited by, or directly resulting from, changes in the organism or its environments.
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. The downside is that you have to go to the vet to get a supply, as they have a prescription-only strangle-hold on the supply of this extremely safe medicine. To make things worse, vets routinely will not give you a supply of this despite breeders knowing that Soloxine is effective in controlling diseases they consider sub-clinical and therefore not suitable to treat with this life-saver.
SUMMARY
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.
In the order of a small p.s.: a typical testimonial, from GSD breeder Andrew Masia. “It’s funny that you bring this up, because when I started breeding about 20 years ago, at the urging of Margaret Iaquinto and Al Stone, I put all my bitches on Soloxine starting about 1 month before their scheduled cycle and continuing on right up to their due date. All of the bitches were in estrus at about 16 to 20 days max with no incidents of a split heat cycle and the smallest litter that I had was 7 pups. It seems as though I have forgotten my past precautions over the last several years and I think that not so coincidentally I have recently seen more split heat cycles and smaller-sized litters. I will have to go back to the basics when my next bitch is nearing her heat.”
