Alteration in Cobalt Absorption in Patients with Disorders of Iron Metabolism

Abstract

In 12 normal control subjects given four oral doses of 20 μmoles of radioactive ferrous chloride or an equimolar amount of radioactive cobaltous chloride followed by an unabsorbable marker, the average excretion of radioactivity in the feces prior to disappearance of the marker was 64 and 54%, respectively. An average of 9% of the iron and 2% of the cobalt was lost in the feces after the marker was passed. The average absorption of iron, 27%, was significantly less than the absorption of cobalt, 44%. The results suggest that the intestinal mucosal uptake of cobalt is slightly greater than that of iron, and cobalt, unlike iron, is not sequestered in the mucosa and subsequently lost with desquamation of the intestinal epithelium. In 6 patients with iron deficiency, the average absorption of iron and cobalt, 60 and 71%, respectively, was significantly increased. A direct correlation was observed between the absorption of iron and cobalt in the control and iron-deficient subjects. In 5 patients with exogenous iron overload, the average percentage absorption of iron, 10%, was markedly reduced whereas the absorption of cobalt was within the range observed in control subjects. The average absorption of both iron and cobalt was increased in 2 patients with cirrhosis associated with iron overload and in 4 patients with idiopathic hemochromatosis. The results demonstrate that cobalt absorption is responsive to the physiological mechanisms that enhance iron absorption but not to those that inhibit it.