Absorption of Iron from the Gastrointestinal Tract A COMPARATIVE STUDY OF THE ORAL IRON TOLERANCE TEST IN HUMAN BEINGS USING STABLE AND RADIOACTIVE IRON

T HE SIGNIFICANCE of changes in serum iron levels after the ingestion of large doses of stable iron has been questioned as a valid index of iron absorption.”2”4 It is apparent that not only the rate of absorption, but also the rate of removal of iron from the blood deter-mines the serum levels. Previous work in this laboratory has utilized an oral iron tolerance test with stable iron in an endeavor to study iron absorption in states of health and disease.5 This study was under-taken in an attempt to evaluate the accuracy of the Ramsey method6 for the determination of serum iron by comparing the recovery of stable iron in the serum after oral administra-tion with the recovery of simultaneously ad-ministered radioactive iron in the serum. Fur-thermore, it was desired to ascertain whether or not these values for serum recovery bear any relationship to the total absorption of Fe’9 as determined both by stool analysis and recov-ery of Fe59 in the hemoglobin