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Category: Cats

The Feline Thyroid Gland: A Model for Endocrine Disruption by PBDEs? (Study Closed)
August 31, 2006 (published)

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Published results can be found here.

Study Start Date: 06/01/2005
Study End Date: 06/30/2007

The Feline Thyroid Gland: A Model for Endocrine Disruption by PBDEs?

Hyperthyroidism in cats (due to a functional thyroid adenoma) suddenly became a commonly recognized clinical syndrome in the late 1970s. The disease generally requires medical or surgical intervention. Although the cause remains unknown, the disease is analogous to toxic multinodular goiter (TMG), or Plummer's disease in humans. While the pathogenesis of TMG is complex, some cases of thyrotoxicosis are thought to arise from chronic overstimulation of an underactive thyroid gland by thyroid stimulating hormone (TSH). Epidemiologic studies of cats in 2000 and 2004 found that advancing age and canned cat foods were positively correlated with hyperthyroidism. Furthermore, certain flavors of canned food (e.g. fish, liver and giblets) and foods in pop-top cans (in males) were implicated.

Polybrominated diphenyl ethers (PBDEs) are flame-retardants that have been manufactured and used extensively since the early 1970s. PBDEs are proven endocrine disruptors, causing hypothyroidism in laboratory animals. They are lipophilic, have long half-lives, and bioaccumulate readily. Based on the etiology of TMG, the epidemiologic data correlating hyperthyroidism and diet, the known endocrine disruptive effect of PBDEs, and the temporal association with the initial use of PBDEs and the recognition of hyperthyroidism, this study aims to: 1) evaluate canned food as a chronic source of exposure of domestic cats to PBDEs, 2) identify a trend from subclinical hypothyroidism to thyrotoxic hyperthyroidism with advancing age, and 3) correlate thyroid function with body burdens of PBDEs.

Sample Size:
40 cats

Inclusion criteria:
10-15 years old, hyperthyroid (diagnosed by elevation of T4 +/- Free T4) with no concurrent illness except dental disease requiring prophylaxis, either pre-or post-therapy (medical or 131I). Serum collection from actively hyperthyroid cats, adipose tissue collection post-medical (or radioactive iodine therapy) stabilization and pre-cachexia.

Informed consent will need to be obtained from clients (see link below.)

Exclusion Criteria:
Concurrent systemic disease (e.g. renal failure); cachexia secondary to hyperthyroidism.

Study Controls:
10-15 years old, euthyroid with no debilitating systemic disease, undergoing elective general anesthesia for dental prophylaxis.

Actively hyperthyroid cats (untreated) - 5mls (if possible) frozen serum (red-top).
Treated hyperthyroid cats - 10gm adipose tissue, frozen in glass jar (available on request).
Clients (owners) - Survey is linked below and can be sent electronically upon request. Clients are requested to submit a house dust sample as well (submitted in a plastic Ziploc-type bag) from a vacuum bag

Documents for Download:
Informational Letter for Clients
Client Consent Form
Client Questionnaire

Each client that participates fully will receive $45
Each clinic that participates will receive $89 for each case, as compensation for time and supplies.

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Full Disclosure information:

  • The study is funded by Waste Management Research Center, Illinois Department of Natural Resources.
  • The investigators do not have any conflict of interest.
  • The study will be published if results are negative.
  • The study will be reported on VIN.
  • The authors will acknowledge VIN if the study is published.
  • Quarterly updates will be provided.

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