Abstract
Florsheirn reported that large doses of thyroid hormone, when employed for suppression of intrinsic TSH in McKenzie assay mice, reduced the response of the animal to TSH or LATS. Accelerated radioiodine clearance was proposed for the mechanism of this reduction in the response. We sought to determine whether thyroidal responsiveness per se is influenced by the dose of thyroid hormone, adopting radioiodine release and intracellular colloid droplet formation as parameters of thyroid response. A daily dose of T3, 0.5, 10, 25 μg, or T4, 0.5 or 25 μg was injected SC into mice for three days after 125I injection. On the day after the last thyroid hormone injection, they received 0.075 mU TSH or LATS-IgG. Blood radioactivity and response index were obtained on the specimens taken before, 2½ or 8 hr after the injection. Colloid droplet counts were obtained on the thyroid gland removed at ½ hr after TSH or 2 hr after LATS-IgG. The dose of TSH or LATS, which caused sizable and significant extent of radioiodine rele...
Published Version
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