1. Monitoring the Effects of Radioiodine Treatment with a Complete Thyroid Panel (T4, T3, Free T4, TSH)

Note that enrollment of new hyperthyroid cats into this study ended on October 1, 2014.

This study investigates the use of a complete thyroid panel of tests (serum T4, T3, free T4, and TSH) to monitor the cats after radioiodine treatment. All cats treated with radioiodine at the Animal Endocrine Clinic will be eligible for this study.

The goal of this study is to determine if measuring a complete panel of four thyroid hormones will be better at detecting mild degrees of thyroid dysfunction in cats that have been treated with radioiodine (I-131). This includes looking for both persistent hyperthyroidism and mild hypothyroidism (an underactive thyroid condition that can develop if too little normal thyroid tissue remains after treatment).

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2. Use of a Complete Thyroid Panel (T4, T3, Free T4, TSH) as an Aid in Diagnosing Iatrogenic Hypothyroidism in Cats

This study investigates the usefulness of a complete thyroid panel of 4 tests to help diagnose hypothyroidism (an underactive thyroid condition) that can develop in hyperthyroid cats after radioiodine treatment.

We anticipate that use of a complete thyroid panel of 4 tests (serum T4, T3, free T4, and TSH) will increase our ability to properly and accurately diagnose hypothyroidism in cats. This diagnosis, however, will be confirmed by thyroid imaging (thyroid scintigraphy), considered the “gold standard” diagnostic technique for thyroid dysfunction.

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3. Evaluation of a Liquid Formulation of L-T4 (Leventa) for Treating Hypothyroidism in Cats

This study investigates the usefulness of a liquid thyroid hormone medication formulation (Leventa® Merck Animal Health; www.leventa.com) for treatment of cats with hypothyroidism (an underactive thyroid condition).

Follow-Up Questionnaire for Owners Whose Cats Are on Leventa

4. Evaluation of the effects of radioiodine treatment on destruction of the hyperthyroid cat’s thyroid tumor with follow-up thyroid scintigraphy

This study investigates the true effectiveness of radioiodine treatment on destruction of the thyroid tumors that all hyperthyroid cats have as the underlying cause of their thyroid disease. At the Animal Endocrine Clinic, we already use thyroid scintigraphy (thyroid scans) to determine the size of each cat’s thyroid tumor. The purpose of this study is to determine if the thyroid tumors are completely destroyed when re-evaluated 3-6 months after treatment.

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5. Effects of the anticonvulsant phenobarbital on serum thyroid hormone concentrations in hyperthyroid and euthyroid cats

Co-investigator: Sofie A. Van Meervenne, DVM, Dipl ECVIM-CA (neurology), Lackeby Animal Hospital, Lackeby, Sweden

In dogs, it is well known that phenobarbital, a drug commonly prescribed for seizure disorders, will result in lowering of the circulating thyroid hormone concentrations. If this same effect occurs in cats is unknown. This study investigates the effect of phenobarbital in hyperthyroid and non-hyperthyroid cats (already being treated with the drug for a seizure disorder) in order to determine if the drug lowers the thyroid levels or if it has no effect.

6. Determination of serum total T4, free T4, total T3, free T3, and reverse T3 by mass spectrometry in hyperthyroid cats before and after treatment

Co-investigators: Federico Fracassi, DVM, PhD, Dipl ECVIM-CA (internal medicine), University of Bologna, Italy; and Marco Caldin, DVM, PhD, Dipl ECVCP, Director San Marco Veterinary Clinic, Padova, Italy

This study investigates a number of circulating thyroid hormone analytes that are not routinely determined in clinical practice. In particular, determination of serum concentrations of reverse T3 might be useful in predicting the presence of concurrent nonthyroidal illness, which is not uncommon in the elderly cat already suffering from hyperthyroidism.

7. Comparison of efficacy of standard (4 mCi) versus lower-dose (2 mCi) I-131 for treatment of cats with mild to moderate hyperthyroidism

Co-investigators: John Lucy, DVM; John F. Randolph, DVM, Dipl ACVIM; Meg Thompson, DVM, Dipl ACVR; Peter V. Scrivani, DVM, Dipl ACVR, and Janet M. Scarlett, DVM, PhD, Cornell University Hospital for Animals, College of Veterinary Medicine, Cornell University, Ithaca, New York.

The amount of radioiodine administered may be based on a fixed dose (4-5 mCi) or a variable dose (determined by severity of clinical signs, size of thyroid gland based on palpation or thyroid imaging, and serum total T4 concentration). At the Cornell University Hospital for Animals, a 4 mCi fixed-dose of I-131 has traditionally been used to treat cats with mild to moderate hyperthyroidism. However, using the variable dose method, Dr. Peterson has discovered that many hyperthyroid cats seem to be successfully controlled with 2 mCi I-131. The purpose of this study is to carefully compare these two I-131 doses (2 mCi at the Animal Endocrine Clinic and 4 mCi at Cornell University) for treatment of feline hyperthyroidism. Each protocol reflects standard of care at the participating facility.

8. Effect of non-thyroidal illness on thyroid stimulating hormone and free thyroxine concentrations by chemiluminescent immunoassays in cats

Co-investigators: Danielle Davignon, DVM; John F. Randolph, DVM, Dipl ACVIM; and Janet M. Scarlett, DVM, PhD, Cornell University Hospital for Animals, College of Veterinary Medicine, Cornell University, Ithaca, New York.

This study will investigate the effect that non-thyroidal illness has on serum thyroid hormone concentrations (including T4, T3, free T4) as well as pituitary thyroid stimulating hormone (TSH). As far as the free T4 assay is concerned, we know that the standard free T4 assay (FT4 by dialysis) can give us high (false positive) results in sick cats. Recently, some labs have changed assay methods and now do their free T4 assay by a chemiluminescent methodology (Immulite). However, no one has looked at how nonthyroidal illness affects those free T4 results. So one of our purposes will be to compare the FT4 results done by the 2 methods to see which is better in cats suffering from nonthyroidal disease.

9. Investigation of intestinal and exocrine pancreatic function amd fecal microbiota in hyperthyroid cats before and after radioiodine treatment

Co-investigator: David A. Williams MA VetMB, PhD, Dipl ACVM and ECVIM-CA, University of Illinois

Gastrointestinal issues (vomiting, diarrhea, soft or voluminous stools) are not uncommon in hyperthyroid cats. This study investigates the effect of feline hyperthyroidism on both intestinal and pancreatic function, and also evaluates the GI microbiota changes associated with successful treatment and restoration of normal thyroid function. To that end, we will evaluate intestinal and pancreatic function by measuring serum cobalamin, folate, and pancreatic lipase immunoreactivity (fPLI), and we will evaluate stool to determine levels of fecal alpha1-proteinase inhibitor and calprotectin. Finally, we will evaluate the fecal microbiota and metabolomics in sera both before and after treatment.

10. Determination of the Environmental Contaminant, bisphenol-A (BPA), in Clinically Normal Cats and Cat with Hyperthyroidism

Co-investigators: Robert C. Backus, DVM, PhD, Dipl. ACVN; and Sara Hooper, DVM, University of Missouri, Veterinary Medical Teaching Hospital, Columbia, MO 65211

The exact cause of hyperthyroidism in cats remains unknown, but many studies have suggested that the contaminant, bisphenol-A (BPA), may contribute to the development of feline hyperthyroidism. The goal of this study is to determine if detected serum levels of BPA can be detected in the feline pet population, and to determine if hyperthyroid cats have higher BPA levels than do normal cats (not suffering from hyperthyroidism). To that end, we will obtain complete dietary and environmental histories from both normal and hyperthyroid cats and collect ~4 ml of blood for determination of serum BPA analysis in these cats.