Biomarkers are various traits which can be used to identify the progress of a disease or condition; they often take a biochemical form. Extensive studies of such traits have allowed scientists to use them very objectively for a wide range of things, ranging from tests for exposure to toxins to early warning signs of cancer. Biomarkers are also used in fields like geology, astronomy, and chemistry for things like dating rocks, understanding chemical reactions, and learning more about the universe. The term is also used in medicine to refer to substances which are studied in a patient or sample and used as a diagnostic tool.
Biomarkers can take a wide variety of forms. For example, some biomarkers can be used to indicate the presence of certain organisms, including a history of their presence even if they no longer exist. A classic example of such a biomarker is an antibody, a substance developed by the body to help it fight disease. Biomarkers can also be used to differentiate cells; some cancer treatments, for example, are designed to target specific cells, using their biomarkers like a tag.
New biomarkers are being discovered all the time. Research on biomarkers can reveal ways to tell if people have taken various drugs, been exposed to dangerous toxins or diseases, and even what part of the world someone has been spending time in. Specific biomarkers are also sometimes used to test for disease susceptibility; for example, certain genetic mutations can indicate an increased risk of some cancers.
In medicine, biomarkers include a wide range of chemicals which can be used to identify various conditions both inside and outside patients. For example, elevated rates of certain enzymes in the blood can indicate problems with liver functions. Elevated enzymes can also indicate problems with cardiac functions. A wide variety of medical tests can screen for biomarkers like proteins, cholesterol, and hormones which may suggest a medical problem.
If you have ever had blood drawn for diagnostic purposes, you have been tested for biomarkers. Biomarkers can also be extracted from things like urine to reveal conditions like pregnancy and diabetes, and some other body secretions such as sweat and saliva can sometimes contain useful biomarkers as well. Typically, discoveries of new biomarkers are widely publicized in the medical community, because they can be incredibly useful tools, not just for doctors but for scientists in general. For example, researchers who suspect that a high birth defect rate is related to the use of specific chemical weapons can search for known biomarkers which indicate exposure to these weapons, and this evidence can be used to treat people and to potentially bring others to justice for using said weapons.