---

      An Overview of Hemoglobin

This brief overview of hemoglobin is not meant to be comprehensive. The goal is to provide sufficient background to make this Web site useful to people unfamiliar with the area. More detailed sources are listed at the bottom of this site and above.

Hemoglobin is a protein that is carried by red cells. It picks up oxygen in the lungs and delivers it to the peripheral tissues to maintain the viability of cells. Hemoglobin is made from two similar proteins that "stick together". Both proteins must be present for the hemoglobin to pick up and release oxygen normally. One of the component proteins is called alpha, the other is beta. Before birth, the beta protein is not expressed. A hemoglobin protein found only during fetal development, called gamma, substitutes up until birth.

Like all proteins, the "blueprint" for hemoglobin exists in DNA (the material that makes up genes). Normally, an individual has four genes that code for the alpha protein, or alpha chain.Two other genes code for the beta chain. (Two additional genes code for the gamma chain in the fetus). The alpha chain and the beta chain are made in precisely equal amounts, despite the differing number of genes. The protein chains join in developing red blood cells, and remain together for the life of the red cell.

The composition of hemoglobin is the same in all people. The genes that code for hemoglobin are identical throughout the world. Occasionally, however, one of the genes is altered by any of a variety of "accidents" that can occur in nature. These alterations in the genes (called "mutations") are very rare. Since genes are inherited, and they contain the information needed to make a protein, if a mutation produces an abnormal hemoglobin gene in a person, the gene will be passed on to his or her children. The children will produce a modified hemoglobin identical to that of the parent. Most mutations in hemoglobin produce no problem. Occasionally, however, the alteration in the protein changes aspects of its behavior. The types of disorders that can result include sickle cell disease.

 

Blood cells are made up of two components. The hemoglobin is in solution inside the cell. The cell is surrounded by a membrane that holds in the hemoglobin. A rough analogy would be a rubber water balloon. The rubber would be the membrane, and the water would be the hemoglobin. The blood types that most of us know, A, B, O, and Rh, are properties of the membrane. The hemoglobin inside the red cells of a person with type O blood and that inside the red cells of a person with type A blood are identical. The analogy would be of water balloons made from blue and red balloons. The color of the ballon would differ, but the material inside (water) would be the same.

The hemoglobin test is an integral part of your health evaluation. The test is used to:

•     measure the severity of anemia or polycythemia,
•     monitor the response to treatment of anemia or polycythemias, and
•     help make decisions about blood transfusions if the anemia is severe.

 

The hemoglobin test is normally ordered as a part of the complete blood count (CBC) (which is ordered for many different reasons, including as a general health screening). The test is also repeated in patients who have ongoing bleeding problems or chronic anemias or polycythemias.

Normal values in an adult are 12 to 18 grams per deciliter (100 milliliters) of blood. Above-normal hemoglobin levels may be the result of:

•     dehydration,
•     excess production of red blood cells in the bone marrow,
•     severe lung disease, or
•     several other conditions.

 

The best source of information about hemoglobin disorders in general are textbooks of medicine. Textbooks of hematology tend to be very detailed, and confusing for people not conversant with the area. Some text books of medicine are:

• Harrison's Principles of Internal Medicine, McGraw-Hill
• The Principles and Practice of Medicine, Appleton, Century, Croftis
• "Hemoglobin: molecular, genetic, and clinical aspects", HF Bunn and B Forget, Saunders, 1986.
•     Come back to our site to find out more.

 

 

 

Name   Comment Verification Code

Comments submitted from other visitors

More posts, Page # :