Library · Physiology
Iron metabolism
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Iron is needed for very different jobs: making DNA, moving electrons inside the cell, and carrying oxygen in the blood. It also has an oddity. Its levels are controlled by absorption alone: the only way to regulate how much iron the body holds is to regulate how much gets in.
That entry happens in the duodenum, the first stretch of the small intestine. There, on the surface of the intestinal cells, the enterocytes, an enzyme called Dcytb converts ferric iron, which is insoluble, into ferrous iron, which can be absorbed. A transporter called DMT1 then carries it into the enterocyte.
The subtle part comes next. To pass from the enterocyte into the blood, iron has only one door: ferroportin. And that door is controlled by a hormone, hepcidin. When hepcidin binds to ferroportin, ferroportin is degraded, the door disappears, and iron stays trapped inside the cell instead of moving into the blood.
In brief
Iron is essential for DNA synthesis, electron transport, and oxygen transport, and body iron levels are controlled by absorption alone.
In the duodenum, the enzyme Dcytb reduces ferric iron to ferrous iron, and the transporter DMT1 carries it into the enterocyte.
Ferroportin is the only exit for cellular iron, and hepcidin controls it: hepcidin binds ferroportin, degrades it, and keeps iron from reaching the blood.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingBiochemistry, Iron Absorption, StatPearlsPublished
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