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News Dr. Peterson lectured to a packed room of veterinarians and technicians on the topic of Management of Subclinical to Very Mild Hyperthyroidism i
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Dr. Peterson lectured to a packed room of veterinarians and technicians on the topic of Management of Subclinical to Very Mild Hyperthyroidism in Cats. |
 This year's CE and the City was another huge success, with over 250 attendees. |
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Dr. Peterson will be lecturing later this month with Dr. Dennis Chew at the New York State Spring Conference. The conference runs from May 16-18 at the Hilton Westchester in Rye Brook, and Dr. Peterson's lecture will be on Saturday the 17th.
There are four tracks available each day covering a host of surgical, dental, pharmacological and medical issues, as well as courses available for your entire veterinary team: practice managers, LVTs, etc. The three-day event features top notch speakers, a massive trade show and the ability to receive 19 CE hours in just three days.
To register, click here. |
Spring New York State Veterinary Conference
Rye Brook, New York, May 17, 2014
Clinical Debate between Drs. Mark E. Peterson and Dennis Chew:
Pitfalls in the diagnosis and treatment of hypercalcemia: interactive case studies |
2014 ACVIM Forum
Nashville, Tennessee, June 4 - 7, 2014
Topics:
• Ultra-low doses of radioiodine are highly effective in restoring euthyroidism without inducing hypothyroidism in most cats with milder forms of hyperthryoidism: 131 cases.
• Advances in feline hyperthyroidism: A strategy to slow progression of concurrent CKD
• Pitfalls and complications in the diagnosis and treatment of thyroid disease in cats |
2014 American Association of Feline Practitioners Annual Conference in Feline Gastroenterology and Endocrinology
Indianapolis, Indiana, September 18 - 21, 2014
Topics:
• Managing cats with idiopathic hypercalcemia
• Nutritional management of endocrine disease in cats
• Diagnostic testing for hyperthyroidism in cats: more than just T4
• What's the best treatment for hyperthyroidism? Antithyroid drugs, surgery, diet, or radioiodine?
• Hyperthyroidism and the kidney: a strategy to slow progression of CRD in treated cats
• Feline hypothyroidism — much more common than you think! |
This Month's Top Post on the Insights Into Veterinary Endocrinology Blog |
My patient is an 8-year old spayed female mixed-Labrador that presented with marked polydipsia and polyuria. Otherwise, she appears to be feeling well; she has a normal appetite, with no weight loss, vomiting, diarrhea, or coughing.
Her initial work-up identified a high total serum calcium of 13.7 mg/dl (reference interval, 8.9-11.4 mg/dl), which was confirmed two days later (repeat calcium, 13.1 mg/dl). The rest of the serum biochemical analysis (including the serum sodium, potassium, urea nitrogen and creatinine) were normal. The results of a complete blood count were normal and a complete urinalysis was also unremarkable, except for a low urine specific gravity (1.010).
Chest and abdominal radiographs were normal.
A complete calcium panel was next performed (1), with the following results:
Serum ionized calcium (iCa) = 1.63 mmol/L (reference interval, 1.25-1.45)
Serum parathyroid hormone (PTH) = 1.0 pmol/L (0.5 - 5.8)
Plasma parathyroid hormone-related polypeptide (PTHrp) = 0.3 pmol/L (<0.5)
How would you recommend that I proceed in the workup of this dog? I'm considering an abdominal ultrasound and bone marrow exam to look for occult lymphoma, and maybe a trial response to asparaginase? |
My Response:
In adult dogs with repeatable hypercalcemia, the two most common causes include primary hyperparathyroidism and malignancy (2,3). Most dogs with primary hyperparathyroidism feel good (normal attitude and appetite), whereas those with hypercalcemia of malignancy tend to be clinically ill (4-7). With the low-normal serum PTH value and measurable (but normal) PTHrp value, neither of those categories can be completely excluded (2,3,8).
With the current assay for PTH employed at DCPAH (1), it's been my observation that a serum PTH value higher than 1 pmol/L is generally consistent with primary hyperparathyroidism and a PTH value lower than 1 is consistent with PTH-independent hypercalcemia (usually neoplasia). However, remember that PTH is a peptide and is subject to breakdown and degradation during shipping, especially if the plasma sample was not kept frozen or at least cool. Therefore, sample handling issues (delay in transit or sample warming) can result in falsely-low serum PTH concentration. If there is any doubt about the sample integrity when it arrived in the lab, a new serum sample should be collected to recheck the PTH concentration. After the serum is collected, it should be immediately frozen and shipped by overnight delivery to the lab (with dry ice or freezer pack) to ensure valid results.
Hypercalcemia associated with Addison's disease is also relatively common in dogs and is possible in this case (9). However, the normal serum concentrations of sodium and potassium and the fact that your dog is not showing signs of serious illness make hypoadrenocorticism unlikely. Most of these hypercalcemic dogs have overt Addison's disease, with moderate to marked hyperkalemia and hyponatremia. That said, you could certainly run a resting cortisol concentration to help exclude hypoadrenocorticism — the finding of a serum cortisol value above 2.0 µg/dl basically rules out Addison's disease (10).
Rare causes of hypercalcemia also include hypervitaminosis D or A and granulomatous disease, so these must be considered (2,3,11,12). Most of the other differentials can be excluded with routine serum biochemical analysis and history (Table 1). |
 Table 1: Differential list for hypercalcemia in dogs |
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Workup for undefined hypercalcemia
There are a number of ways to handle this case. Here is a workup list for you to consider, starting with the easiest and least invasive:
1. Perform thorough rectal exam to rule out an anal sac adenocarcinoma (13-15).
2. Carefully check for lymph node enlargement and aspirate any lymph nodes that you can palpate.
3. Measure a resting cortisol concentration to help exclude hypoadrenocorticism. If the basal cortisol concentration is low, this should be followed up with an ACTH stimulation test to confirm Addison's disease (10).
4. Consider repeating the serum PTH concentration. Since lipemia can effect the results, the dog should be fasted overnight. After blood collection, allow serum to clot at room temperature for 30 to 60 min prior to separation. The serum sample should be immediately frozen and shipped by overnight delivery to the lab (with dry ice or freezer pack) for PTH analysis (1).
5. If the repeat PTH value is above 1.0 pmol/L (in other words, not suppressed) consider having an experienced radiologist perform a cervical ultrasound exam looking for a parathyroid nodule, which would more strongly suggest primary hyperparathyroidism (16).
6. If the repeat PTH value is suppressed or if the cervical ultrasound fails to detect a parathyroid tumor, then consider a complete abdominal ultrasound examination to screen for possible occult cancer, especially lymphoma.
7. Collect multiple aspirates of the liver and spleen with ultrasound-guidance, even if those organs appear normal on your ultrasound exam. I've had cases in which the ultrasound exam appears normal but the cytology said otherwise.
8. Consider a bone marrow aspirate. However, given the normal hematology results, this is less likely to be diagnostic.
9. Finally, if all of the above fails to yield a definitive diagnosis, then consider monitoring the ionized calcium and PTH concentrations to make sure that the hypercalcemia does not rapidly progress and that the PTH value remains stable. If the PTH value increases to the mid-normal to high range, that finding would be most consistent with primary hyperparathyroidism; on the other hand, if the value falls further, that would be consistent with PTH-independent hypercalcemia (e.g., malignancy) (2,3).
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Bottom Line:
If nothing is found on your complete workup, I've learned that close observation and monitoring is sometimes the best route to take. This includes periodic exams (including lymph node palpation and rectal exams), as well as following the serum iCa concentrations. I've had a few dogs with persistent, but stable, idiopathic hypercalcemia in which a definitive cause for the hypercalcemia was never identified. But the dogs (and eventually the owners) didn't care all that much, since the degree of hypercalcemia remains fairly stable and was not very progressive.
By contrast, in those dogs that have progressive disease and develop severe, worsening hypercalcemia, the underlying cause will eventually be obvious, even if it isn't apparent during the initial workup. |
• Broome MR, Peterson ME, Walker JR. Clinical features and treatment outcomes of 41 dogs with sublingual ectopic thyroid neoplasia. Journal of the American Veterinary Medical Association (submitted)
• Bargellini P, Orlandi R, Dentini A, Paloni C, Rubini G, Fonti P, Peterson ME, Boiti C. Differentiation of adrenal mass lesions in dogs by contrast-enhanced ultrasound. Journal of the American Animal Hospital Association. (submitted)
• Peterson ME, Broome MR. Thyroid scintigraphy findings in 2,096 cats with hyperthyroidism. Veterinary Radiology & Ultrasound 2013 (in press, early view online version available here)
• Peterson ME, Eirmann L. Dietary management of feline endocrine disease. Veterinary Clinics of North American: Small Animal Practice 2014 (in press)
• Peterson ME. Diagnosis and management of iatrogenic hypothyroidism, In: Little SE, ed. August's Consultations in Feline Internal Medicine: Elsevier, 2014 (in press).
• Broome MR, Peterson ME. Treatment of severe, unresponsive, or recurrent hyperthyroidism. In: Little SE, ed. August's Consultations in Feline Internal Medicine: Elsevier, 2014 (in press).
• Broome MR, Peterson ME. Using thyroid hormone supplementation to preserve kidney function in cats with concurrent renal disease after treatment for hyperthyroidism. In: Little SE, ed. August's Consultations in Feline Internal Medicine: Elsevier, 2014 (in press).
• Peterson ME: Advances in the treatment of feline hyperthyroidism: a strategy to slow the progression of CKD. Proceedings of the 2014 American College of Veterinary Internal Medicine (ACVIM) Forum. 2014 (in press).
• Peterson ME: Hyperthyroidism, In: Greco D, Davidson A(eds), Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Endocrinology and Reproduction. Ames, Iowa, Wiley-Blackwell. 2014; (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). |
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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