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Thyroid Stimulating Hormone (TSH), produced by the pituitary gland, regulates the production of thyroid gland hormones, hormones which affect almost every function in the body. TSH stimulates the production of more thyroid hormones if the pituitary gland senses that circulating levels are too low; less hormones if levels are sensed as being too high. Although the test for TSH concentration has successfully been in use for a number of years in humans, its application for dogs has not been available in laboratories until this last year. As of February, 1995, this TSH test became available at the Animal Health Diagnostic Laboratories--the prestigious laboratories of the Michigan State University, using a method developed by Section Chief of Endocrinology, Dr. Raymond Nachreiner, DVM, Ph.D., while he attended the Swedish University of Agricultural Sciences in Upsala, Sweden, during a 6-month sabbatical leave. This test gives a more comprehensive and accurate picture of the functioning of a dog's thyroid gland than simply using the T3 and T4 tests which measure the circulating levels of thyroid hormones. A useful example might be when T3 and T4 tests are at the very low end of the normal scale--technically within normal limits. According to Dr. Nachreiner, if these values are then coupled with a high TSH level, you may instead have a thyroid gland that is actually malfunctioning--i.e., the signal (TSH) from the pituitary gland is telling the thyroid gland to produce more hormones, and the thyroid gland's best effort is only the very low reading produced by the T3 and T4 tests. Thyroid supplementation is probably indicated. Dr. Nachreiner states that symptoms of low thyroid output (hypothyroidism) are: obesity, nonspecific skin problems, hair loss, alopecia (baldness), seborrhea, chronic infections of ears or skin, "heat-seeking" behavior, occasional occurrence of dark pigmentation on the skin, and sometimes infertility. The Animal Health Diagnostic Laboratory recommends that a complete thyroid panel be performed if your veterinarian suspects hypothyroidism. Part of the thyroid panel which Michigan State performs is an auto antibody test. If the auto antibody is present in the dog's blood sample, says Dr. Nachreiner, it automatically suggests auto immune thyroiditis--most likely Hashimoto's Thyroiditis. A 1993 study he cites indicated that 16 out of 190 tested Basenjis (a little over 8%) were positive for the autoimune antibody indicating auto immune thyroiditis. The bad news, however, is that dogs who test positive for the auto antibody may show aberrant results in other areas of thyroid testing, even falsely elevated concentrations. Dr. Nachreiner cautions that veterinarians need to use their own judgment as to whether the dogs has chronic illness or debilitation, is taking glucocorticoids, is eating goitrogenic foods, has a lack of iodine in its diet, etc. all of which would alter thyroid function and tests. If no recognizable reason seems to exist for the dog's symptoms, it might be reasonable to suggest that a complete thyroid panel, possibly including the more expensive dialysis testing on the dog's submitted blood sample, be done to clarify the actual state of the thyroid. The Michigan State University's laboratory address is: Animal Health Diagnostic Laboratories, P.O. Box 30076, Lansing, MI 48909, phone: (517) 353-0621. Dr. Nachreiner, D.V.M., Ph.D., Section Chief of Endocrinology, or his colleagues Dr. Refsal and Graham, would be happy to answer any questions your veterinarians may have. Article copyright © 2001 by Betsy Polglase. |