Hemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs.
Hemoglobin is made up of four protein molecules (globulin chains) that are connected together. The normal adult hemoglobin (abbreviated Hgb or Hb) molecule contains two alpha-globulin chains and two beta-globulin chains. In fetuses and infants, beta chains are not common and the hemoglobin molecule is made up of two alpha chains and two gamma chains. As the infant grows, the gamma chains are gradually replaced by beta chains, forming the adult hemoglobin structure.
Each globulin chain contains an important iron-containing porphyrin compound termed heme. Embedded within the heme compound is an iron atom that is vital in transporting oxygen and carbon dioxide in our blood. The iron contained in hemoglobin is also responsible for the red color of blood.
Hemoglobin also plays an important role in maintaining the shape of the red blood cells. In their natural shape, red blood cells are round with narrow centers resembling a donut without a hole in the middle. Abnormal hemoglobin structure can, therefore, disrupt the shape of red blood cells and impede their function and flow through blood vessels.
How is hemoglobin measured?
Hemoglobin is usually measured as a part of the routinecomplete blood count (CBC) test from a blood sample.
Several methods exist for measuring hemoglobin, most of which are done currently by automated machines designed to perform different tests on blood. Within the machine, the red blood cells are broken down to get the hemoglobin into a solution. The free hemoglobin is exposed to a chemical containing cyanide that binds tightly with the hemoglobin molecule to form cyanomethemoglobin. By shining a light through the solution and measuring how much light is absorbed (specifically at a wavelength of 540 nanometers), the amount of hemoglobin can be determined.
What are normal hemoglobin values?
The hemoglobin level is expressed as the amount of hemoglobin in grams (gm) per deciliter (dL) of whole blood, a deciliter being 100 milliliters.
The normal ranges for hemoglobin depend on the age and, beginning in adolescence, the gender of the person. The normal ranges are:
- Newborns: 17 to 22 gm/dL
- One (1) week of age: 15 to 20 gm/dL
- One (1) month of age: 11 to 15 gm/dL
- Children: 11 to 13 gm/dL
- Adult males: 14 to 18 gm/dL
- Adult women: 12 to 16 gm/dL
- Men after middle age: 12.4 to 14.9 gm/dL
- Women after middle age: 11.7 to 13.8 gm/dL
All of these values may vary slightly between laboratories. Some laboratories do not differentiate between adult and "after middle age" hemoglobin values. Pregnant females are advised to avoid both high and low hemoglobin levels to avoid increasing risks of stillbirths (high hemoglobin – above the normal range) and premature birth or low-birth-weight baby (low hemoglobin – below the normal range).
What does a low hemoglobin level mean?
A low hemoglobin level is referred to as anemia or low red blood count. A lower than normal number of red blood cells is referred to as anemia and hemoglobin levels reflect this number. There are many reasons (causes) for anemia.
Some of the more common causes of anemia are:
- loss of blood (traumatic injury, surgery, bleeding,colon cancer, or stomach ulcer),
- nutritional deficiency (iron, vitamin B12, folate),
- bone marrow problems (replacement of bone marrow by cancer),
- suppression by red blood cell synthesis bychemotherapy drugs,
- kidney failure, and
- abnormal hemoglobin structure (sickle cell anemia or thalassemia).
What does a high hemoglobin level mean?
Higher than normal hemoglobin levels can be seen in people living at high altitudes and in people who smoke.Dehydration produces a falsely high hemoglobin measurement that disappears when proper fluid balance is restored.
Some other infrequent causes are high hemoglobin levels are:
- advanced lung disease (for example, emphysema);
- certain tumors;
- a disorder of the bone marrow known aspolycythemia rubra vera, and;
- abuse of the drug erythropoietin (Epogen) by athletes for blood doping purposes (increasing the amount of oxygen available to the body by chemically raising the production of red blood cells).
With special thanks to www. MedicineNet.com
No comments:
Post a Comment