The Determination of Iron Absorption and Loss by Whole Body Counting

A technic for the study of radioiron absorption and loss is described employing an NaI (T1) crystal-detector whole body counter and 1-10 µc. Fe59 in 250 µg. elemental iron. Changes in whole body Fe59 activity during the first few hours and the next 90-100 days after oral ingestion are described and their significance discussed. Normal absorption with this technic ranges from 5.7-24.7 per cent of the administered tracer. In 14 patients with polycythemia vera, 12 previously phlebotomized and 2 with a recent history of gastrointestinal hemorrhage, iron deficiency as evidenced by increased iron absorption (20.6 per cent-96.9 per cent) correlates well with the extent of preceding phlebotomy, and relatively well with the plasma iron at the time of study. Although other parameters reflect iron deficiency, none correlate well with the absorption of radioiron. Next to increased iron absorption, depletion of iron stores in the marrow seems to be the earliest evidence of iron deficiency. Iron absorption and erythrocyte incorporation of radioiron was also studied in several other hematologic disorders, including four heavily menstruating women, three cases of aplastic anemia, and a small number of other conditions. The findings are described and discussed. Radioiron loss in three normal patients was 0.110 per cent, 0.110 per cent, and 0.182 per cent daily, and in two patients with aplastic anemia 0.103 per cent and 0.173 per cent daily, defining the normal range of tracer loss over days 20-100. Radioiron loss in the polycythemics ranged from 0-0.044 per cent daily. An unusual case of pyridoxine-responsive anemia with increased absorption of radioiron (69.1 per cent), but no red cell incorporation, lost only 0.026 per cent/day. Some problems in the interpretation of such data are discussed. The results demonstrate the effectiveness of the technic of whole body counting in the study of various aspects of iron metabolism.