Iron and Total Iron Binding Capacity (TIBC)
The serum iron test measures the amount of iron in your blood. The total iron-binding capacity (TIBC) test looks at how well the iron moves through your body.
The serum iron test measures the amount of iron in your blood. The total iron-binding capacity (TIBC test) test looks at how well the iron moves through your body.
Why is Iron Important for Health?
Iron is an important mineral that your body needs to stay healthy. Your body uses iron to make hemoglobin, the protein in your red blood cells that carries oxygen throughout your body. If you don't have enough iron, you may not have enough hemoglobin. This condition is called iron deficiency anemia.
Iron in your body is carried, or bound, mainly to a protein made by your liver called transferrin. The TIBC test is based on certain proteins, including transferrin, found in the blood. Your transferrin levels are almost always measured along with iron and TIBC.
Iron plays a principal role in erythropoiesis, the formation and maturation of red blood cells (RBCs) and is required for hemoglobin synthesis. The human body contains between four and five grams of iron, about 65% of which is present in hemoglobin and 3% of which is present in myoglobin, the oxygen storage protein found in skeletal muscle and cardiac muscle. A small amount is also found in cellular enzymes that catalyze the oxidation and reduction of iron. Excess iron is stored in the liver and spleen as ferritin and hemosiderin. Any iron present in the serum is in transit between the digestive track and bone marrow, and available iron stores forms. Sixty to 70% of the body's iron is carried by its specific transport protein, transferrin. For this reason, total iron binding capacity (TIBC) and transferrin are sometimes referred to interchangeable, even though other proteins carry iron and contribute to the TIBC.
Unbound iron is highly toxic, but there is generally an excess of transferrin available to prevent the buildup of unbound iron in the circulation. The percentage of iron saturation is calculated by dividing the serum iron value by the TIBC value and multiplying it by 100.
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.
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. 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, 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.
Symptoms of Low Iron:
Symptoms of iron deficiency can occur even before the condition has progressed to iron deficiency anemia.
Symptoms of iron deficiency are not unique to iron deficiency. Iron is needed for many enzymes to function normally, so a wide range of symptoms may eventually emerge, either as the secondary result of the anemia, or as other primary results of iron deficiency. Symptoms of iron deficiency include:
- hair loss
- brittle or grooved nails
- hair thinning
- Plummer–Vinson syndrome: painful atrophy of the mucous membrane covering the tongue, the pharynx and the esophagus
- impaired immune function
- pagophagia (compulsive ice chewing)
- restless legs syndrome
Continued iron deficiency may progress to anemia and worsening fatigue. Thrombocytosis, or an elevated platelet count, can also result. A lack of sufficient iron levels in the blood is one reason that some people cannot donate blood.
High Iron- Iron Overload
Iron overload or hemochromatosis indicates accumulation of iron in the body from any cause. The most important causes are hereditary haemochromatosis (HHC), a genetic disorder, and transfusional iron overload, which can result from repeated blood transfusions.
Organs most commonly affected by haemochromatosis include the liver, heart, and endocrine glands.
Hemochromatosis may present with the following clinical syndromes:
- liver: chronic liver disease and cirrhosis of the liver.
- heart: heart failure, cardiac arrhythmia.
- hormones: diabetes (see below) and hypogonadism (insufficiency of the sex hormone producing glands) which leads to low sex drive and/or loss of fertility in men and loss of menstrual cycle in women.
- metabolism: diabetes in people with iron overload occurs as a result of selective iron deposition in islet beta cells in the pancreas leading to functional failure and cell death.
- skeletal: arthritis, from calcium pyrophosphate deposition in joints leading to joint pains. The most commonly affected joints are those of the hands, particularly the knuckles of the second and third fingers.
- skin: melanoderma (darkening or 'bronzing' of the skin).
- The skin's deep tan color, in concert with insulin insufficiency due to pancreatic damage, is the source of a nickname for this condition: "bronze diabetes"
What Can the Iron and TIBC Test Diagnose?
- Assist in the diagnosis of iron deficiency anemia.
- Differentiate between iron deficiency anemia and anemia secondary to chronic disease.
- Monitor hematological response to therapy during pregnancy and iron deficiency anemias.
- Provide support for diagnosis of hemochromatosis or diseases of iron metabolism and storage.
What Can Increase Iron Test Levels?
- Acute liver disease.
- Hypochromic iron-deficiency anemias.
- Late pregnancy.
- Testosterone therapy via increased hemoglobin and hematocrit.
What Can Decrease Iron Test Levels?
Iron is decreased in chronic infections, cirrhosis, hemochromatosis, hemolytic anemias, neoplastic diseases, protein depletion, renal disease, excessive menstruation, frequent blood donations and internal bleeding.
What Medications Can Increase or Decrease TIBC Test Results?
- Drugs that may increase TIBC levels include mestranol and oral contraceptives.
- Drugs that may decrease TIBC levels include which is asparaginase, corticotropin, cortisone, and testosterone.
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