Use of recombinant human thyroid-stimulating hormone for thyrotropin stimulation testing in euthyroid ferrets

Abstract

To evaluate the effects of IM administration of recombinant human thyroid-stimulating hormone (rhTSH) on plasma total thyroxine (T4) concentrations in euthyroid ferrets. Evaluation study. 25 healthy neutered ferrets (14 female and 11 male) of various ages from 2 populations (laboratory ferrets from Georgia and pet ferrets from Pennsylvania). Each ferret underwent a physical examination and standard hematologic testing to ensure it was healthy and had clinically normal thyroid function. Once determined to be euthyroid, ferrets received a single IM injection of 100 μg of rhTSH. Blood samples were collected into plasma-separator tubes immediately before the rhTSH injection (time 0) and 4 hours after injection to measure T4 concentrations. Males did not differ from females in regard to prestimulation or poststimulation plasma T4 concentrations; however, prestimulation and poststimulation T4 concentrations were significantly different between the 2 groups of ferrets. A significant difference was also identified between prestimulation T4 concentration (mean ± SD, 21.3 ± 6.1 nmol/L) and poststimulation T4 concentration (29.9 ± 8.2 nmol/L). All 25 ferrets had high poststimulation T4 concentrations (median difference, 7. 5 nmol/L; 10% to 90% interval, 3.26 to 17.70 nmol/L [0.25 to 1.38 μg/dL]; range, 2.50 to 20.70 nmol/L [0.19 to 1.61 μg/dL]); this represented a median increase in T4 concentration of 35% (10% to 90% interval, 18% to 81%; range, 8% to 126%). Results suggested that rhTSH can be used for thyrotropin stimulation testing in ferrets when administered IM. According to the findings, a euthyroid ferret should have an increase of approximately 30% in plasma T4 concentration 4 hours after rhTSH injection.