John Cargill on Thyroid
This is excerpted from letter written by John Cargill to Lisa Nicolello in answer to her questions on thyroid. Permission to reprint received from Mr. Cargill, MA, MBA, MS; and Lisa Nicolello.
Your question concerning thyroid is not an easy one to answer; however, I will make a stab at it. Thyroid dysfunction shows up very unmistakably in reproductive prowess. Low sperm counts can often be attributed to a low thyroid level, and/or the presence of T3 and T4 autoantibodies. The Michigan State University thyroid panel gives the autoantibody readings. These, in good breeding stock of any breed should be virtually zero. Some of the other values are subject to interpretation -- some say "by breed" but I sort of doubt that. The difference is not so much in the minor genetic variations between breeds, but more the difference in the quality of the selection process for breeding based upon the mind set of the various parent clubs. No one would ever accuse the Bulldog people of taking care of their breed through careful genetic selection!
The approach I have taken, and obviously the one I would recommend is that of following the guidance of Drs. Priscilla Stockner, MS, MBA, DVM, Veterinary Management Services/Canine Cryobank and W. Jean Dodds, Director, Veterinary Hematology Laboratory, New York State Department of Health. Thyroid affects the whole body, and dysfunction as in "hypo-" can upset the clotting times as in acquired vWD. The NORMAL ranges and IDEALS FOR BREEDING PURPOSES are as follows:
TEST RANGE IDEAL TT4 22-54 > 38 TT3 1.2-3.1 > 2.2 FT4 12-39 > 25 FT3 2.2-4.8 > 3.5 T4A < 25 < 10 T3A < 10 < 5These "ideal" figures are just that. Note that the MS after Dr. Stockner's name stands for Master of Science in Reproductive Physiology, which makes her a most unusual veterinarian. Her clinical experience allowed her to come up with the ideals for breeding. Given that nothing else is wrong, she fully expects a satisfactory impregnation and delivery on dogs of all breeds which meet or exceed the ideal scores. Those which meet or exceed the ideal scores also tend to have large healthy litters without producing any runts. Just to give you an idea of how some dogs fare on these tests and their history, Ch. Kobu's Kyrion, our resident stud and Ch. Kobu's Ka-aba, CD, Alpha Bitch, and Ch. Krimson whose largest litter was also 11 and who has conceived with frozen semen, are shown below. Ka-aba was RWB at our nationals one year, and she and Kyrion together have taken a couple of BIS Braces. Krimson took RWB at the nationals following Ka-aba. Ka-aba's litters and Krimson's litters have been very uniform in size, varying less than 2 ounces from the largest pup to the smallest pup. We have yet to have an Akita pup fail to make height.
TEST IDEAL KA-ABA KRIMSON KYRION TT4 > 38 30 61.2 69.4 TT3 > 2.2 1.7 1.5 2.8 FT4 > 25 18.9 24.8 28.4 FT3 > 3.5 4.4 5.2 7.4 T4A < 10 10 6 5 T3A < 5 0 0 0The most indicative tests for present or future thyroiditis are the T4A and T3A autoantibody tests. These show whether any immune system cells (T-Cells, phagocytes, etc.) are attacking the thyroid gland. Notice that while not all of the values are within the ideal range in every test on a given dog, with the exception of our resident stud, Kyrion, they are well within the acceptable ranges. It may also be that because of flea dips, etc., being on the show circuit, immunizations, etc., that the thyroid values are depressed at the time the blood samples were taken. I have seen dogs with minimal sperm counts go to high sperm counts after flea season is over and they are no longer being dipped. This is an indication that the immune system has been depressed. Ivermectin, for example, will definitely lower both sperm counts and thyroid levels.
I have to caution you that the ideals are Dr. Stockner's opinion of what constitutes the ideal for breeding. To be within the normal range and not up to her ideal does not mean that the animal should not be used for breeding purposes -- it is only a goal, and one that is generally unobtainable for any given animal. The ideals are useful in determining, for instance, whether to keep an animal that will not finish its championship, but could be used for breeding. A ripped ear in a fight, an injury to foot or shoulder, etc., are good examples why such an animal might not have a show career, but would be very useful for breeding stock. All else being equal, go for the animal with the better thyroid scores. If those in your line are low, then by all means, sacrifice some of the aesthetic characteristics of the standard and go with the animal that will produce health and longevity.
Be aware that some animals with very high T4A and T3A and low thyroid levels may still carry good coat, and be able to breed. This does not mean that they should be used. We look at the thyroid panel as a major input to considering whether to breed an animal or not. We do not like flea allergies, and a good strong thyroid function seems to reduce allergic responses of all sorts. This makes sense as we are dealing with something that has such a large impact on the immune system, and allergies are nothing more than an immune system making wrong choices either in terms of intensity of response or in selecting the wrong targets.
In response to your question as how to rate dogs as normal, go for the published ranges established by Michigan State University. They are the owners of the database; they have done quite a bit of work on that database, and they are the only ones around with a validated lab protocol that has been held consistent for large numbers of tests conducted. Do not let anyone fool you into thinking that breeds are different in their normal range just because of poor genetic selections. For most things, dogs are dogs are dogs and there is very little genetic difference between them. Thus, one would expect with careful breeding to see the same values amongst all the breeds and varieties. One would expect to see the values coming out the same as for feral dogs, coyotes, etc. I have picked on Bulldogs enough, so let me pick on something else. How about German Shepherds? Their problems are legendary, and can only be overcome by careful corrective genetic selection, but there are German Shepherds out there who meet all the ideals in terms of thyroid function.As for putting dogs on thyroid medication -- that is a case of fooling oneself. Might as well go for plastic surgery.
You asked whether we had problems in the Akita fancy of people refusing to test for various things. Of course we do; however, the trend in advertising is certainly towards a full and complete genetic screening. I like to think that my articles have had some impact. Certainly, in two years, I have seen the numbers of advertisements showing more than just hip x-rays, go from almost none to almost all in the Akita World. Let me take a break and go and get one. Found one, here on my desk: May/June, 1992 Akita World. In 69 pages of advertisements, the number of pages in which hip x-rays/OFA, eyes/CERF, thyroid or vWD were mentioned are as follows:
Advertisements 68 Hips/OFA 18 Eyes/CERF 12 Thyroid 6 vWB 3In other months, more recent, the ratios have been higher for thyroid and vWD. This particular month just happened to have a lot of ads for spring born puppies. So, yes, the word is getting out and a number of people are passing out copies of my Truth in Advertising and Genetic Screening. I think it is making a difference. Just keep advertising that you are doing the screening. I give prospective puppy buyers a listing of things they should ask for from a breeder. Most of them have to do with genetic screening. Then I ask them to check with other breeders, and consider why they should settle for less when the price differential is minimal or non-existent. Who wants to dump lots of money into a sick dog. If some one were to ask me, I wouldn't even want to dump a lot of money into a sick wife. Shows where I stand! Firmly and forever on the side of genetic screening prior to making any breeding choices.
Should you need more information, I would refer you directly to Dr. Stockner.
Additional text of the letter refers to specific dogs belonging to Lisa, referencing his Novem- ber, 1991 article "CryoPup" with the suggestion that storage/freezing of sperm of any genetically clear, champion, obedience titled dogs would be well worth the effort to preserve a healthy gene pool.
...It is hard enough to get a healthy and long-lived Mastiff in the first place. It is hard enough to get a champion with a CD, let alone a CDX. You have a valuable commodity that is rapidly depreciating. I would think that those genes are too valuable to loose. Remember, not all sperm banks are equal. You might find it worthwhile to find your way out to California. Note: they (Canine Cryobank/Escondido, CA) will collect and store one of your dogs free (for one year) upon presentation of AKC championship, CERF, OFA, normal Thyroid and vWD. That is how rare such animals are! I would imagine that normal hips, thyroid and vWD are few and far between in Mastiffs. Sad, isn't it, especially given that it does not have to be this way.
Statistician and retired Marine officer, John Cargill is involved in continuing medical education with the Osler Institute in Terre Haute, Ind. and an Akita breeder in Bonsall, CA. He is a frequent contributor to Dog World Magazine and we would like to thank him immensely for his insights on thyroid dysfunction.