Development of an experimental model of hypothyroidism in cockatiels (Nymphicus hollandicus)

Craig A. Harms From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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James J. Hoskinson From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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David S. Bruyette From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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James W. Carpenter From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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John Galland From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Jobna K. Veatch From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Sandra C. Wilson From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Jeffrey G. Baier From the Departments of Clinical Sciences (Harms, Hoskinson, Bruyette, Carpenter, Galland, Wilson, Baier) and Veterinary Diagnostic Investigation (Veatch), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Summary

Hypothyroidism is 2 possible predisposing factor in a number of disorders of companion psittacine birds. We developed and validated a thyroid-stimulating hormone (tsh) response testing protocol for cockatiels (Nymphicus hollandicus), using 0.1 IU of tsh/bird given IM, with blood sample collection at 0 and 6 hours after tsh, and a commercial radioimmunoassay for thyroxine (T4). This protocol was used to document a seasonal sex difference in stimulated T4 values— females responded with higher T4 values than those in males in summer—and a stress-induced depression of baseline T4 values was detected in a group of cockatiels with normal tsh response. An experimental model for mature-onset hypothyroidism in cockatiels was created by radiothyroidectomizing cockatiels with 3.7 MBq (100 μCi) of 131I/bird given IV. Induction of the hypothyroid state was confirmed by baseline T4 concentration, tsh response test results, thyroid pertechnetate scintigraphy, and gross and microscopic examinations. Classical signs of hypothyroidism (eg, hypercholesterolemia, obesity, poor feathering) were lacking or mild at 48 days after thyroid ablation.

Summary

Hypothyroidism is 2 possible predisposing factor in a number of disorders of companion psittacine birds. We developed and validated a thyroid-stimulating hormone (tsh) response testing protocol for cockatiels (Nymphicus hollandicus), using 0.1 IU of tsh/bird given IM, with blood sample collection at 0 and 6 hours after tsh, and a commercial radioimmunoassay for thyroxine (T4). This protocol was used to document a seasonal sex difference in stimulated T4 values— females responded with higher T4 values than those in males in summer—and a stress-induced depression of baseline T4 values was detected in a group of cockatiels with normal tsh response. An experimental model for mature-onset hypothyroidism in cockatiels was created by radiothyroidectomizing cockatiels with 3.7 MBq (100 μCi) of 131I/bird given IV. Induction of the hypothyroid state was confirmed by baseline T4 concentration, tsh response test results, thyroid pertechnetate scintigraphy, and gross and microscopic examinations. Classical signs of hypothyroidism (eg, hypercholesterolemia, obesity, poor feathering) were lacking or mild at 48 days after thyroid ablation.

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