Iron deficiency
Iron deficiency, or sideropenia, is the state in which a body lacks enough iron to supply its needs. Iron is present in all cells in the human body and has several vital functions, such as carrying oxygen to the tissues from the lungs as a key component of the hemoglobin protein, acting as a transport medium for electrons within the cells in the form of cytochromes, and facilitating oxygen enzyme reactions in various tissues. Too little iron can interfere with these vital functions and lead to morbidity and death.[1]
For other uses, see Iron deficiency (disambiguation).Iron deficiency
Sideropenia, hypoferremia
Total body iron averages approximately 3.8 g in men and 2.3 g in women. In blood plasma, iron is carried tightly bound to the protein transferrin. There are several mechanisms that control iron metabolism and safeguard against iron deficiency. The main regulatory mechanism is situated in the gastrointestinal tract. The majority of iron absorption occurs in the duodenum, the first section of the small intestine. A number of dietary factors may affect iron absorption. When loss of iron is not sufficiently compensated by intake of iron from the diet, a state of iron deficiency develops over time. When this state is uncorrected, it leads to iron-deficiency anemia, a common type of anemia.[1] Before anemia occurs, the medical condition of iron deficiency without anemia is called latent iron deficiency (LID).
Anemia is a condition characterized by inadequate red blood cells (erythrocytes) or hemoglobin. When the body lacks sufficient amounts of iron, production of the protein hemoglobin is reduced. Hemoglobin binds to oxygen, enabling red blood cells to supply oxygenated blood throughout the body. Women of child-bearing age,[2] children, and people with poor diet are most susceptible to the disease. Most cases of iron-deficiency anemia are mild, but if not treated can cause problems like an irregular heartbeat, pregnancy complications, and delayed growth in infants and children that could affect their cognitive development and their behavior.[3][4]
Bioavailability[edit]
Iron is needed for bacterial growth making its bioavailability an important factor in controlling infection.[16] Blood plasma as a result carries iron tightly bound to transferrin, which is taken up by cells by endocytosing transferrin, thus preventing its access to bacteria.[17]: 30 Between 15 and 20 percent of the protein content in human milk consists of lactoferrin[18] that binds iron. As a comparison, in cow's milk, this is only 2 percent. As a result, breast-fed babies have fewer infections.[17] Lactoferrin is also concentrated in tears, saliva and at wounds to bind iron to limit bacterial growth. Egg white contains 12% conalbumin to withhold it from bacteria that get through the egg shell (for this reason, prior to antibiotics, egg white was used to treat infections).[17]: 29
To reduce bacterial growth, plasma concentrations of iron are lowered in a variety of systemic inflammatory states due to increased production of hepcidin which is mainly released by the liver in response to increased production of pro-inflammatory cytokines such as interleukin-6. This functional iron deficiency will resolve once the source of inflammation is rectified; however, if not resolved, it can progress to anaemia of chronic inflammation. The underlying inflammation can be caused by fever,[19] inflammatory bowel disease, infections, chronic heart failure (CHF), carcinomas, or following surgery.
Reflecting this link between iron bioavailability and bacterial growth, the taking of oral iron supplements in excess of 200 mg/day causes a relative overabundance of iron that can alter the types of bacteria that are present within the gut. There have been concerns regarding parenteral iron being administered whilst bacteremia is present, although this has not been borne out in clinical practice. A moderate iron deficiency, in contrast, can provide protection against acute infection, especially against organisms that reside within hepatocytes and macrophages, such as malaria and tuberculosis. This is mainly beneficial in regions with a high prevalence of these diseases and where standard treatment is unavailable.
As always, laboratory values have to be interpreted with the lab's reference values in mind and considering all aspects of the individual clinical situation.
Serum ferritin can be elevated in inflammatory conditions; so a normal serum ferritin may not always exclude iron deficiency, and the utility is improved by taking a concurrent C-reactive protein (CRP). The level of serum ferritin that is viewed as "high" depends on the condition. For example, in inflammatory bowel disease the threshold is 100, where as in chronic heart failure (CHF) the levels are 200.
Cancer research[edit]
The presence of Helicobacter pylori in the stomach can cause inflammation and can lower the threshold for the development of gastric cancer. In the setting of iron deficiency, H. pylori causes more severe inflammation and the development of premalignant lesions.[40] This inflammatory effect appears to be mediated, in part, through altered bile acid production including an increase in deoxycholic acid, a secondary bile acid implicated in colon cancer and other gastrointestinal cancers.[40]