When the body is low on iron, the heart makes more hepcidin, which might help protect the heart from damage during iron deficiency.

In the heart, the way hepcidin responds to iron levels is different from how it works in the liver - when the body is low on iron, the heart makes more hepcidin protein even though the gene for it is less active.

Giving iron directly into the bloodstream of mice with heart cell hepcidin deficiency stops their hearts from failing, proving that the heart problems are caused by the heart cells not getting enough iron.

Heart cells make and release hepcidin using a process that requires the enzyme Furin, and they release more of it when the body is low on iron.

When mice lose the ability to make hepcidin in their heart cells, their heart cells don't get enough iron, which causes their hearts to weaken and eventually fail, even though their overall body iron levels are normal.

When female mice can't make a protein called hepcidin, they end up with too much iron in their blood and body, and their red blood cell numbers go up — this suggests hepcidin normally keeps iron levels in check.