Iron Homeostasis

Describe the normal nutritional requirements

Approximately 3-5g of iron is found in the body as:

Oxygen-carrying globin molecules
Haemoglobin (~70%) and myoglobin (~5%).
Catalyst for biological reactions (~25%)
Catalase, peroxidase, and cytochromes all require iron.

Absorption

Dietary iron comes in two forms:

Haeme groups
Directly absorbed via specialised transport proteins.
Dietary iron salts
- Ferrous (Fe²⁺) iron is soluble, and is absorbed via facilitated diffusion across the enterocyte membrane
  - Reduced acidity of the stomach will reduce the absorption of ferrous iron
- Ferric (Fe³⁺) iron precipitates when pH > 3, and so cannot be absorbed independently by the small bowel.
  - A pathway may exist for absorption of ferric iron from soluble chelates

Once in the enterocyte, iron can be:
- Stored, bound to ferritin
- Transported via ferroportin out of the enterocyte, where it is then oxidised to ferrous iron and bound to transferrin

Excretion is uncontrolled
Regulation of iron levels is only by absorption
Hepcidin is a liver protein which inhibits the action of ferroportin
- High hepcidin prevents iron transport from the enterocyte
- Hepcidin is deficient in haemochromatosis

Chambers D, Huang C, Matthews G. Basic Physiology for Anaesthetists. Cambridge University Press. 2015.

Last updated 2017-09-23