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Thyroid growth immunoglobulins in feline hyperthyroidism
R S Brown1, P Keating, P G Livingston
1Department of Pediatrics, University of Massachusetts Medical School, Worcester.
Thyroid : Official Journal of the American Thyroid Association
|January 1, 1992
Summary
Thyroid growth-stimulating antibodies (IgGs) are present in hyperthyroid cats, similar to human goiter. These IgGs promote thyroid cell growth via the TSH receptor but do not increase thyroid function.
Area of Science:
- Endocrinology
- Immunology
- Veterinary Medicine
Background:
- Feline hyperthyroidism shares similarities with human toxic nodular goiter.
- The role of circulating thyroid antibodies in thyroid growth is under investigation.
Purpose of the Study:
- To investigate the effect of immunoglobulin (Ig) G from hyperthyroid cats on thyroid cell growth.
- To determine if these IgGs interact with the TSH receptor.
Main Methods:
- Purified IgG preparations from hyperthyroid cats were applied to a rat thyroid follicular (FRTL-5) cell line.
- Assays included [3H]-thymidine incorporation, cellular proliferation, TSH receptor binding, and cAMP stimulation.
Main Results:
- Hyperthyroid cat IgG significantly increased DNA synthesis and stimulated cellular proliferation 15-fold.
- This growth stimulation was inhibited by a TSH receptor blocking antibody.
- Hyperthyroid cat IgG inhibited TSH binding to thyroid membranes but did not stimulate cAMP production.
Conclusions:
- Elevated titers of thyroid growth-promoting IgGs, likely acting via the TSH receptor, are present in feline hyperthyroidism.
- These IgGs may contribute to goiter formation in cats.
- Thyroid hyperfunction in feline hyperthyroidism is not dependent on these growth-promoting IgGs.