Effect of Oral Thyroxine and Tri-Iodo-Thyronine on Radioactive Iodine Uptake and Serum Protein Bound Iodine in Normal Human Subjects

Abstract

Sodium-levo-thyroxine in dosage of 0.075 mg., orally, usually reduced radioactive I uptake by the thyroid of normal human subjects; this was associated with a rise of protein bound I when a dosage of 0.2 mg. or more was given. Tri-iodo-thyronine in dosage as low as 0.008 mg. orally also reduces the uptake. This is associated with a decrease in serum protein bound I.