Animal Endocrine Clinic seminar in Westchester on March 18
The March 18th Animal Endocrine Clinic Seminar was a resounding success! Dr. Peterson delivered four lectures to an audience of over 80 veterinarians from the tri-state area. To see images from the March 18 Seminar, click here. To sign up for Dr. Peterson's email list, click here.
Dr. Peterson was recently interviewed by Steve Dale (Steve Dale's Pet World) on the treatment options available for hyperthyroid cats.
Continuing Education lecture
East End Veterinary Emergency & Specialty Center
Riverhead, New York, April 3, 2012
Call (631) 369-4513 or email DrVatash@pet-ER.com for more information.
* Hyperadrenocorticism: From Confusion to Clarity
CE & the City
New York, New York, May 19, 2012
* Hyperthyroidism and Thyroid Tumors in Cats and Dogs: Pitfalls in Diagnosis and Treatment
2012 ACVIM Forum
New Orleans, Louisiana, May 30 - June 2, 2012
* The Problem Diabetic: Acromegaly, Cushing’s, and Other Causes of Insulin Resistance
Patty is an 8-year-old female neutered Boston Terrier who was referred to Dr. Peterson for evaluation of a suspected thyroid tumor (Figure 1). Eight months before referral, Patty was examined because of lethargy and a dull, patchy hair coat. Routine laboratory testing was normal except for the finding of a low serum T4 concentration.
Further workup with a complete thyroid panel revealed low serum concentrations of total and free T4 and a high cTSH value (Table 1), diagnostic for hypothyroidism. Patty was started on hormone replacement with levothyroxine (L-T4; 0.1 mg, BID).
Table 1: Pretreatment serum thyroid results
Over the next 3 months, Patty‘s lethargy and hair coat improved markedly on the L-T4 replacement therapy. Six-hour post-pill monitoring of her serum thyroid hormone values revealed high-normal levels of total T4 and free T4 with low-normal serum TSH concentrations, consistent with a well-controlled hypothyroid dog (Table 2).
However, Patty's post-pill values for both total T3 and free T3 were both extremely elevated (Table 2). Based upon these high T3 results, a T3-secreting thyroid tumor was suspected and Patty was referred to the Animal Endocrine Clinic.
Table 2: Post-pill serum thyroid results on L-T4 supplementation
On presentation to the Animal Endocrine Clinic, the owners noted that Patty has been doing well but had lost weight (approximately 1 pound) since the L-T4 had been started. A mild increase in thirst and urination was also noted.
On physical examination, Patty was bright and alert. Her body condition score was 3/5 with a body weight of 21 pounds. The heart rate was normal with no murmurs or arrhythmias. No thyroid nodules or masses were detected on cervical (neck) palpation. In order to best evaluate Patty's thyroid gland function and anatomy, Dr. Peterson temporarily discontinued Patty's L-T4 medication for 2 weeks in preparation for thyroid scintigraphy (thyroid scan procedure).
Repeat history 2 weeks later revealed some improvement in Patty's thirst and urination. No change in body weight or overall physical exam was noted.
One hour after administration of a small tracer dose of radioactivity, thyroid scintigraphy was performed. Patty was an excellent patient, allowing us to complete the scan with no sedation (Figure 2). Results of the thyroid scan revealed that neither thyroid lobe was visible, consistent hypothyroidism (Figure 3). No ectopic thyroid tumors were identified on thyroid scintigraphy.
Figure 2: Dr. Peterson and Patty after completion of her thyroid scan.
Figure 3: Notice the lack of thyroid tissue on this scan. The normal location of the 2 thyroid lobes is indicated by the yellow ovals.
Because the thyroid scan ruled out a thyroid tumor, we next measured T4 and T3 autoantibodies, which are known to produce spurious elevations in thyroid hormone levels in dogs with hypothyroidism. The results of Patty's T4 antibodies were low, but the T3 antibody index was very high at 45% (reference range, 0-10%), confirming the presence of circulating T3 autoantibodies.
Comments
This dog illustrates 2 important points. First of all, thyroid hormone autoantibodies may falsely increase measured T3 and T4 concentrations in dogs. Such autoantibodies are uncommon; the results of one study found that T3 autoantibodies were present in 57 of 1,000 dogs with hypothyroidism whereas T4 autoantibodies were found in only 17 of 1,000 dogs (1).
In dogs, these antibodies which cross-react with T4 and/or T3 are markers for lymphocytic thyroiditis. Although these antibodies indicate underlying thyroid gland pathology and have a large effect in the laboratory test tube, they do not influence the availability or delivery of thyroid hormone in dogs treated with L-T4. In this dog, it is highly likely that the T3 autoantibodies were present at time of initial diagnosis of hypothyroidism (pretreatment T3 levels were never measured), but the presence of the autoantibodies did not interfere with the response to L-T4.
Secondly, although rarely considered as a diagnostic test, both ultrasonography and scintigraphy of the thyroid gland can be very useful in confirming the diagnosis of hypothyroidism in dogs (2-4). With an experienced radiologist, use of thyroid sonography (i.e., decreased echogenicity and decreased thyroid volume) can be an effective ancillary diagnostic tool to differentiate between canine hypothyroidism and euthyroid sick syndrome. The best imaging technique, however, is the use of technetium 99m (99m-Tc) uptake and scintigraphy of the thyroid gland (3,4). In one study, thyroid scintigraphy was found to be the best diagnostic test for hypothyroidism, providing the least overlap between dogs with primary hypothyroidism and dogs with nonthyroidal illness (3).
Top 10 Cat and Dog Medical Conditions of 2011 Veterinary Pet Insurance Co. (VPI), the nation's oldest and largest provider of pet health insurance, recently sorted its database of more than 485,000 insured pets to determine the top 10 dog and cat medical conditions in 2011.
FDA Video: Safe Handling of Pet Food in the Home This week the U.S. Food and Drug Administration’s Center’s for Veterinary Medicine released a new video that cautions consumers about the health dangers — in the form of food-borne illness and disease—associated with feeding pet foods.
Book Review —The Cat: Clinical Medicine and Management This book, which is a completely revised version of the edition last published in the mid-1990s, is a welcome addition the library for any veterinary office that cares for cats.
The Animal Endocrine Clinic is the only clinic of its kind in the country that specializes in the diagnosis and treatment of cats and dogs with endocrine disorders. Dr. Peterson has set up two NY clinics (Manhattan and Bedford Hills) to service clients from New York City, Long Island, Westchester County, New Jersey and Connecticut.
This Clinic is separated into three divisions: the Endocrine Clinic, dedicated to diagnosing and treating dogs and cats with endocrine disorders; the Hypurrcat treatment center designed for treating hyperthyroid cats with radioactive iodine (I-131); and Nuclear Imaging for Animals, a state-of-the-art medical imaging facility where we use radioactive tracers to perform nuclear scanning (scintigraphy) for diagnosing of thyroid, bone, liver, and kidney diseases in dogs and cats.
The Animal Endocrine Clinic is a referral-only hospital, and does not offer prophylactic or routine care. We can be reached by phone at (212) 362-2650 or (914) 864-1631; by email at info@animalendocrine.com or on the web at www.animalendocrine.com.
