THYROID ACTIVITY AFTER IODINE INGESTION

Abstract

When rats, kept in a refrigerator for 3 wks. are given 20-25 mg. NaI per day, an elevation in B.M.R. occurs which is as great as that found in control rats. After being placed in a warm environment the metabolism of these rats returns to the control level more quickly if they are given Nal. The ingestion of NaI does not depress the metabolism of normal rats unless the amt. given is large enough to cause inanition. The withdrawal of large doses of NaI (in most cases 160 mg. per day) frequently depresses basal metabolism for several wks. thereafter. The withdrawal of smaller doses of NaI (20-25 mg. per day) does not bring about a measurable reduction in metabolism. It does prevent the occurrence of as large an elevation of metabolism as that ordinarily produced by either thyrotrophic principle or prolonged exposure to cold. When thyrotrophic principle is given and followed by prolonged exposure to cold, the metabolic response is greater than that produced by either stimulus alone.