Alteration in thyroid hormone and gastrin concentrations in goats infected with Trichostrongylus colubriformis

Abstract

Five groups of five goats each were infected with 0, 10, 25, 40 or 50 × 10 3 third-stage larvae of Trichostrongylus colubriformis. On days 0, 7, 14, 21 and 28 after infection, serum samples were collected and assayed for thyroxine (T 4), triiodothyronine (T 3), thyroid binding globulin and gastrin. Immediately after collection of baseline samples, thyrotropin releasing factor (TRF) (1 μg/kg body weight) was administered intravenously. Additional serum samples were collected 1 and 4 hr later and assayed for T 3 and T 4, respectively. Significant alterations of thyroid hormone concentrations in goats were associated only with the duration of infection, and not with the magnitude of the infective inoculum. Thyroid binding globulin and gastrin concentrations were not altered by the size or duration of T. colubriformis infection. TRF significantly increased ( P<0.001) mean levels of T 4 (from 4.6 to 8.0 μg/dl at 4 hr) and T 3 (from 0.6 to 1.91 ng/ml at 1 hr). Intravenous administration of 1 μg/kg TRF with collection of serum 1 and 4 hr later proved a suitable regime for thyroid stimulation testing in the goat.