Analysis of serum or plasma total T4 concentration is considered a first-line test when an animal is suspected of having hypothyroidism or hyperthyroidism.1–3 Although these endocrinopathies are not common in ferrets (Mustela putorius furo), the authors have encountered ferrets in which thyroid disease was highly suspected. Case reports4–6 of ferrets with disease of the thyroid gland have been published in the peer-reviewed literature; however, the antemortem diagnosis of thyroid disease in ferrets is challenging because of limited diagnostic options.
The radioimmunoassay method is often used for measurement of plasma total T4 concentration in companion animals.7 A benefit of the radioimmunoassay is that it can be performed with a small volume (25 μL) of plasma, which is particularly useful for small exotic animal species in which blood volume is limited. Although the diagnostic approach for domestic small animals in which hypothyroid disease is suspected includes measurement of plasma total T4 concentration, TSH concentration, autoantibody titer, and free T4 concentration by equilibrium dialysis and possibly TSH stimulation testing, many of these tests have not been evaluated for use in exotic pets.
For dogs and cats suspected to have thyroid disease, it has been customary to use bovine TSH for TSH stimulation testing; however, bovine TSH is no longer available as a pharmaceutical preparation and has been replaced with the considerably more expensive rhTSH. Because of this development, new protocols for TSH stimulation testing in companion animals have been established with the use of rhTSH instead of bovine TSH. Protocols have been described for dogs and cats,8,9 but we are not aware of a similar protocol for ferrets.
The purpose of the study reported here was to evaluate the effects of IM injection of rhTSH on plasma T4 concentration in euthyroid ferrets with the aim of developing an antemortem method for evaluation of thyroid gland function in ferrets. The specific hypotheses were that rhTSH could be safely and effectively used for TSH stimulation testing of ferrets, an increase in plasma T4 concentration would occur in ferrets given rhTSH, and no significant difference between the sexes or between ferret populations would be identified in plasma T4 concentrations before or after rhTSH administration.
Recombinant human thyroid-stimulating hormone
Thyrogen, Genzyme Corp, Cambridge, Mass.
Coat-a-Count, Siemens Healthcare Diagnostics, Los Angeles, Calif.
SPSS, version 18.0, SPSS Inc, Chicago, Ill.
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