Thyroxine Biosynthesis and Thyroidal Uptake of I 131 in Rats at The Onset of Hypoxia Exposure. ∗

Abstract

Summary

Exposure of rats to a reduced pressure (380 mm Hg) simulating an altitude of 18,000 feet resulted in a markedly elevated I¹³¹ uptake in the thyroid, a relative increase in the amount of intrathyroidal I¹³¹ MIT and a lowered I¹³¹ DIT. The hypoxia induced alteration of thyroid hormone synthesis was found to be a transient response since the I¹³¹ MIT/DIT ratio returned to control levels after 60 hours of exposure. A possible mechanism which could account for these thyroidal changes is discussed.