Iron, a Janus-face element

Part 2: Doping G. Jacobasch, M. Bauer-Marinović, Nuthetal Regulatory mechanisms keep not only the concentrations of alkali cations but also of iron constant. Since iron is bound to transport proteins, its concentration is exclusively controlled by intestinal absorption and not by renal function. This mechanism is subject to a complex system of interacting controlling factors. Whether iron absorption is to be increased or decreased in the enterocyte is signalled by hepcidine, a peptide hormone, synthesised in the liver. In case of insufficient supply of oxygen to the tissues, the rate of erythropoiesis is increased by release of the hormone erythropoietin. It inhibits the production of hepcidin and, thus, its negative (oder blocking) influence on iron absorption. If there is no need for iron, hepcidine synthesis is induced by the protein of the hemochromatosis gene, HFE, resulting in decreasing iron absorption. Top-performance athletes outwit the complex control system of iron homeostasis by direct or simulated training at high altitudes and, more effectively, by doping to increase erythropoiesis and thus achieve utmost ATP formation in muscle tissue. This results in an accumulation of iron in the organism. The iron overload even grows after the athletes have retired from sports as long excessive iron is not removed by withdrawal of blood. Clinical manifestation, diagnostic parameters and therapeutic strategies are explained for the case of primary hemochromatosis.  The risk of a pathological iron excess is increased in men with a genetic defect in the hemochromatosis gene. This applies to 15 % of the German population. A clinical manifestation of hemochromatosis is prevented by early diagnosis and removal of excessive iron by bloodlettings. It should always be kept in mind that iron concentrations near the lower limit are less dangerous to the human organism than those near, or exceeding, the upper limit. Keywords: Iron / requirement / absorption / metabolism Sie finden den Artikel in deutscher Sprache in Ernährungs-Umschau 06/04 ab Seite 231.