Effect of Epinephrine on Radioiodide Uptake by the Normal Human Thyroid

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Abstract
Subcutaneous epinephrine, 0.01 mg/kg body weight, was given to normal subjects at various times before and after intravenous radioiodide for 1- and 2-hr uptake measurement. Paired control experiments were performed. Epinephrine did not affect thyroidal uptake when it was given 30 min after radioiodide or when the 2 substances were given simultaneously. When epinephrine was given 30–60 min before dioiodide, uptake was stimulated, and at 24 hr uptake had returned to control values. An intravenous infusion of pinephrine (12.8 μg/min) from 30 to 90 min after radioiodide injection caused a significant depression in the rate of thyroidal accumulation of radioactivity during the infusion. The depression of uptake after epinephrine may be due to decreased thyroidal clearance of plasma radioiodide, to a relative decrease in the radioiodide concentration in the plasma being cleared, or to both these factors. The cause for the rebound stimulation of uptake seen 5 hr after epinephrine is unknown.