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News Dr. Peterson was recently appointed to the Editorial Board of a new journal called Veterinary Sciences. Veterinary Sciences is an international
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Dr. Peterson was recently appointed to the Editorial Board of a new journal called Veterinary Sciences.
Veterinary Sciences is an international, scientific, open access journal on veterinary medicine, which will be published online on a quarterly basis. The first issue will be released early in 2014. |
Third Annual GEMFE Congress on Feline Medicine, Seville, Spain, February 1 - 2, 2014
Topics:
• What's the best treatment for hyperthyroidism? Antithyroid drugs, surgery, diet, or radioiodine ?
• Hyperthyroidism and the kidney: A love-hate relationship
• Treatment of severe, unresponsive, or recurrent hyperthyroidism in cats
• Feline hypothyroidism — Much more common than you think!
• The difficult diabetic: Acromegaly, Cushing’s & other causes of insulin resistance
• Nutritional management of endocrine disease in cats |
 Figure 1: Daisy, 12-year old female Labrador Retriever with hyperthyroidism |
Daisy is a 12-year-old, female spayed Labrador Retriever weighing 72 pounds who was referred to Dr. Peterson for evaluation of hyperthyroidism of unknown cause (Figure 1).
Three months before referral, Daisy was examined for her annual recheck. The owner reported that she was doing very well; the body weight was stable, with no clinical signs. Routine laboratory testing was normal except for the finding of a slightly high serum T4 concentration (5.4 µg/dl; reference range, 0.8-3.5 µg/dl). |
Recheck examination failed to reveal any palpable masses in the thyroid region, but repeat thyroid testing confirmed high serum concentrations of both T4 (5.1 µg/dl) and free T4 (50 pmol/L; reference range, 5-40 pmol/L). Further questioning of the owner revealed that Daisy had been receiving a daily fish oil supplement, as well as a daily treat containing kelp, which is high in iodine content. Since Daisy was not showing any clinical signs of hyperthyroidism and no obvious thyroid tumor was palpable, the owners were instructed to stop the kelp and fish oil supplements and recheck a complete serum thyroid panel in 6 weeks.
On recheck examination 2 months later, no change in clinical features were reported. However, a right cervical nodule could now be palpated. Results of a complete thyroid panel again confirmed slightly high serum concentrations of T4 (5.2 µg/dl), T3 (180 ng/ml), and free T4 (53 pmol/L), with undetectable levels of TSH (<0.03 ng/ml). Serum T4 and T3 autoantibodies and thyroglobulin autoantibodies were all negative. Because of the persistent hyperthyroidism (i.e., high T4, T3, free T4; low TSH), which did not resolve after stopping the iodine supplement, Daisy was referred to the Animal Endocrine Clinic for thyroid scintigraphy.
Results of the thyroid scintigraphy revealed increased radionuclide uptake in an enlarged right thyroid lobe (see DV view in Figure 2m below). The normal left lobe was completely suppressed and could not be visualized. The thyroid:salivary gland ratio (normally a 1:1 ratio) was also very high at 6.2, which confirmed that the right thyroid tumor was hyperfunctional and was responsible for Daisy's hyperthyroidism. On the thyroid scan, there was no evidence of soft tissue invasion or tumor metastasis to the lungs. Results of thoracic radiography revealed a normal heart size;in agreement with the scintigraphy findings, no pulmonary metastasis was detected. |
 Figure 2: Thyroid scintigraphy (dorsal-ventral and lateral views) performed on Daisy, showing a moderate-sized, hyperfunctional thyroid tumor. Notice the complete suppression of the left normal thyroid lobe. |
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Based on these thyroid scan findings, the diagnosis was hyperfunctional thyroid tumor (most likely thyroid adenoma), leading to mild hyperthyroidism. Surgical exploratory with removal of the right thyroid tumor was scheduled. Preoperative preparation with methimazole (10 mg/day) was initiated, which was administered for 2 weeks prior to thyroidectomy.
At surgery, the right lobe of the thyroid gland was very vascular and enlarged. The left thyroid lobe appeared to be slightly small and did not appear to be affected. The right thyroid lobe was easily resected; no local soft tissue invasion was noted. The incision was closed in a routine manner and Daisy recovered without complication. Histopathological examination of the tumor tissue revealed a follicular adenoma.
Follow-up contact with the owner 3 months later revealed that Daisy continues to do well, with no complications of the surgery. A repeat serum T4 concentration was now well within reference range limits (1.5 µg/dl), confirming cure of the hyperthyroid state.
Comments
Thyroid neoplasia is relatively uncommon in the dog, accounting for approximately 2% of all canine tumors and 10-15% of tumors of the head and neck (1-3). The majority of thyroid tumors detected clinically are malignant, of which 10% are hyperfunctional and secrete excess amounts of thyroid hormone (2-5). In contrast to hyperthyroid cats, most canine thyroid adenomas are clinically rare, usually discovered at necropsy as an incidental finding. Only 2 dogs with hyperthyroidism secondary to benign thyroid adenoma have previously been reported (6,7).
In this dog, the high serum thyroid hormone concentrations (total and free T4) and suppressed TSH value confirmed hyperthyroidism, while the negative thyroid hormone autoantibodies ruled out thyroiditis (3,5). Serum T4 and T3 autoantibodies have been reported to lead to spurious elevations in measured T4 and/or T3, but this was ruled out preoperatively based on the finding of negative autoantibodies.
Reported signs of canine hyperthyroidism include weight loss, tachycardia, polydipsia, polyuria, none of which were reported in this dog. Only the geriatric thyroid screening picked up this dog's preclinical hyperthyroid state, allowing for early diagnosis and treatment of a potentially malignant tumor. If a high serum T4 concentration is found in a middle-aged to older dog, a thyroid tumor should be suspected, even if no obvious clinical signs of hyperthyroidism are reported.
In dogs like Daisy, use of thyroid scintigraphy has many advantages over other imaging modalities for dogs with suspected thyroid tumors (8-11). Unlike other imaging procedures, which can only access anatomy, thyroid scintigraphy assesses both organ structure and function. This functional imaging is the strength of nuclear scintigraphy; it can readily detect disease at an earlier stage than anatomical imaging procedures can.
References
1. Leav I, Schiller AL, Rijnberk A, et al. Adenomas and carcinomas of the canine and feline thyroid. Am J Pathol 1976;83:61-122.
2. Barber LG. Thyroid tumors in dogs and cats. Vet Clin North Am Small Anim Pract 2007;37:755-773.
3. Peterson ME. Hyperthyroidism and thyroid tumor in dogs In: Melian C, Perez Alenza MD, Peterson ME, et al., eds. Manual de Endocrinología en Pequeños Animales (Manual of Small Animal Endocrinology). Barcelona, Spain: Multimedica, 2008;113-125.
4. Rijnberk A. Thyroid tumors and hyperthyroidism in dogs In: Rijnberk A, ed. Clinical Endocrinology of Dogs and Cats. Dordrecht/Boston. Kluwer Academic Publishers, 1996;55-59.
5. Mooney CT. Canine hyperthyroidism In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;86-91.
6. Lawrence D, Thompson J, Layton AW, et al. Hyperthyroidism associated with a thyroid adenoma in a dog. J Am Vet Med Assoc 1991;199:81-83.
7. Itoh T, Kojimoto A, Nibe K, et al. Functional thyroid gland adenoma in a dog treated with surgical excision alone. J Vet Med Sci 2007;69:61-63.
8. Mitchell M, Hurov L, Troy G. Canine thyroid carcinomas: clinical occurrence, staging by means of scintiscans, and therapy in 15 cases Vet Surg 1979;8:112–118.
9. Branam JE, Leighton RL, Hornof WJ. Radioisotope imaging for the evaluation of thyroid neoplasia and hypothyroidism in a dog. J Am Vet Med Assoc 1982;180:1077-1079.
10. Marks SL, Koblik PD, Hornof WJ, et al. 99mTc-pertechnetate imaging of thyroid tumors in dogs: 29 cases (1980-1992). J Am Vet Med Assoc 1994;204:756-760.
11. Shiel RE, Pinilla M, McAllister H, et al. Assessment of the value of quantitative thyroid scintigraphy for determination of thyroid function in dogs. J Small Anim Pract 2012;53:278-285.
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Top Endocrine Publications of 2012: Canine and Feline Reproductive Endocrinology
Listed below are 23 research papers written in 2012 that deal with a variety of issues of clinical importance in reproductive endocrinology in dogs and cats.
Diagnostic Testing for Ovarian Remnant Syndrome in Dogs — Is There a Practical Test?
Layla is a 7-year old obese Golden retriever that had an ovariohysterectomy about 5 years ago.
Protocol for ACTH Stimulation Testing to Monitor Dogs on Trilostane Therapy: Timing, Feeding, and ACTH Preparation All Matter
I have a question about the use of ACTH stimulation testing in dogs we are monitoring on Vetoryl (trilostane) therapy.
Testing for Retained Testicular Tissue in Neutered Cats with Urine Marking
My patient is a 5-year-old neutered, male DLH that presented for inappropriate urination.
Trilostane, Prednisone, and ACTH Stimulation Testing in Dogs with Cushing's Disease
Buddy first developed diabetes, which was difficult to control because of insulin resistance.
Top Endocrine Publications of 2012: Feline Diabetes Mellitus
Listed below are 23 research papers written in 2012 that deal with a variety of topics and issues mainly related to the diagnosis, monitoring, and treatment of diabetes mellitus in cats.
Difficult Swallowing in Cats with Hyperthyroidism
We have a 13-year old male cat named Balki with hyperthyroidism and moderate renal disease.
Review of the BSAVA Manual of Canine and Feline Endocrinology, 4th Edition
The BSAVA Manual of Canine and Feline Endocrinology, coedited by Drs. Carmel Mooney and Mark Peterson, received a favorable review by Dr. Krista Visser ‘t Hooft in the November issue of the Journal of Small Animal Practice.
Can a Special Diet be Formulated to Treat Hyperthyroidism in Cats?
I have a 13-year old female DSH cat that has recently been diagnosed with hyperthyroidism. |
• Peterson ME, Eirmann L. Dietary management of feline endocrine disease. Veterinary Clinics of North American: Small Animal Practice 2014, in press
• Peterson ME, Broome MR. Ultra-low dose radioiodine therapy is effective in cats with mild hyperthyroidism. Journal of Veterinary Internal Medicine 2014, in press
• Broome MR, Peterson ME, Kemppainen RJ, Parker VJ, Richter K. Exogenous thyrotoxicosis secondary to the consumption of commercially available all-meat dog food or treats. Journal of Veterinary Internal Medicine 2014, in press
• Rosenthal KL, Peterson ME: Hyperadrenocorticism in the ferret. In: Bonagura JD, Twedt DC (eds): Current Veterinary Therapy V. Philadelphia, Saunders Elsevier, in press
• Kintzer PP, Peterson ME. Differential diagnosis of hyperkalemia and hyponatremia in dogs and cats. In: Bonagura JD, Twedt DC (eds): Current Veterinary Therapy V. Philadelphia, Saunders Elsevier, in press
• Kintzer PP, Peterson ME. Hypoadrenocorticism in dogs. In: Bonagura JD, Twedt DC (eds): Current Veterinary Therapy V. Philadelphia, Saunders Elsevier, in press
• Meleo KA, Peterson ME. Treatment of insulinoma in the dog, cat, and ferret. In: Bonagura JD, Twedt DC (eds): Current Veterinary Therapy V. Philadelphia, Saunders Elsevier, in press
• Peterson ME, Broome MR. Radioiodine for hyperthyroidism. In: Bonagura JD, Twedt DC (eds): Current Veterinary Therapy V. Philadelphia, Saunders Elsevier, in press
• Peterson ME: The Parathyroid Glands and Disorders of Calcium Metabolism, In: Alello, S (ed), The Merck Veterinary Manual (Ninth Ed), Merial, Ltd, in press
• Peterson ME: The Thyroid Gland, In: Alello, S (ed), The Merck Veterinary Manual (Ninth Ed), Merial, Ltd, in press
• Peterson ME. Diagnosis and management of iatrogenic hypothyroidism In: Little SE, ed. August's Consultations in Feline Internal Medicine: Elsevier, in press |
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. |
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