Blood Testing and Glossary
The chief protein constituent in plasma (the liquid component of whole blood), primarily made in the liver.
ALT / SGPT (Alanine Aminotransferase)
An enzyme found mostly in the liver. Smaller amounts are also in the kidneys, heart, and muscles. Under normal conditions, ALT levels in the blood are low. Many drugs may raise ALT levels by causing liver damage in a very small percentage of patients taking the drug. This is true of both prescription drugs and some “natural” health products.
AST / SGOT (Aspartate Aminotransferase)
An enzyme found mostly in the heart and liver, and to a lesser extent in other muscles. When liver or muscle cells are injured, they release AST into the blood. Tests and findings help healthcare practitioners study liver function. AST can also be ordered, either by itself or with other tests, for persons who might have been exposed to hepatitis viruses; those who drink alcohol; persons who have a history of liver disease in their family; or persons taking prescribed or other drugs that can occasionally damage the liver.
Bilirubin is an orange-yellow pigment found in bile. Red blood cells (RBCs) normally degrade after 120 days in the circulation. At this time, a component of the RBCs, hemoglobin (the red-colored pigment of red blood cells that carries oxygen to tissues), breaks down into unconjugated bilirubin. Approximately 250 to 350 mg of bilirubin is produced daily in a normal, healthy adult, of which 85% is derived from damaged or old red cells that have died, with the remaining amount from the bone marrow or liver. In combination with other tests, bilirubin tests are performed to assess liver status, liver disease, bile duct blockage, hemolytic anemia, or a liver-related metabolic problem.
BNP (Brain Natriuretic Peptide)
Also known as: B-type Natriuretic peptides; Brain natriuretic peptide, proBNP. Formal name: B-type natriuretic peptide, N-terminal pro b-type natriuretic peptide. Related tests: Cardiac biomarkers. Either BNP or NT-proBNP may be used to help diagnose heart failure and to grade the severity of that heart failure. However, heart failure is still often confused with other conditions. BNP and NT-proBNP levels can help healthcare practitioners differentiate between heart failure and other problems, such as lung disease.
BUN (Blood Urea Nitrogen)
This test measures the amount of urea nitrogen in the blood. Nitrogen, as ammonia, is produced in the liver when protein is broken into amino acids and metabolized. The nitrogen combines with other molecules in the liver to form the waste product urea. The urea is then released into the bloodstream and carried to the kidneys where it is filtered out of the blood and excreted in the urine. Since this is an ongoing process, there is usually a small but stable amount of urea nitrogen in the blood. BUN tests are used to evaluate kidney function and monitor the effectiveness of dialysis and other treatments related to kidney disease or damage. The test for BUN is performed as part of a routine comprehensive or basic metabolic panel.
One of the most important minerals in your body, calcium is essential for the proper functioning of muscles, nerves, and the heart and is required in blood clotting and in formation of bones. The body goes to great lengths to protect blood calcium levels, and will actually “steal” calcium from the body to maintain blood calcium levels, which leads to osteoporosis. About 99% of calcium is found in the bones while the remainder circulates in the blood. Blood calcium is tested to screen for, diagnose, and monitor a range of conditions relating to the bones, heart, nerves, kidneys, and teeth. Blood calcium levels do not directly tell how much calcium is in the bones, but rather, how much calcium is circulating in the blood. A total calcium level is often measured as part of health screening. It is included in the Comprehensive Metabolic Panel (CMP) and the Basic Metabolic Panel (BMP) – groups of tests that are performed together to diagnose or monitor a variety of conditions.
HDL-Cholesterol, LDL-Cholesterol, Chol/HDL ratio, VLDL-C; Triglycerides (Lipid Profi le) – All of these studies assess the risk of atherosclerosis in the patient.
A waste product produced in muscles from the breakdown of a compound called creatine. Creatine is part of the cycle that produces energy needed to contract your muscles. Creatinine tests are routinely part of a comprehensive or basic metabolic panel; if your healthcare practitioner suspects that you are suffering from kidney dysfunction or if you are acutely or chronically ill with a condition that may affect your kidneys and/or be exacerbated by kidney dysfunction; at intervals to monitor treatment for kidney disease or kidney function while on certain medications. Creatinine tests are also used to screen for dehydration, congestive heart failure, atherosclerosis, or complications of diabetes. Creatinine can also increase temporarily as a result of muscle injury.
CRP & hs-CRP (C-Reactive Protein)
A protein made by the liver and secreted into the bloodstream. It can be measured with two different tests: the CRP test and the high-sensitivity CRP (hs-CRP) test, each measuring different ranges of CRP levels in the blood. The hs-CRP test can more accurately detect lower concentrations of the protein (it is more sensitive) than the standard CRP test. CRP increases with inflammation and infection as well as following a myocardial infarction (MI, heart attack), surgery, and trauma. It is now believed that inflammation plays a major role in atheroslcerosis (the narrowing of blood vessels due to build-up of cholesterol and other lipids), which is often associated with cardiovascular disease (CVD).
DHEA-S (Dehydroepiandrosterone Sulfate)
A hormone produced by the adrenal glands. DHEAS, testosterone, and several other androgens are used to evaluate adrenal function and to distinguish androgen-secreting conditions that are caused by the adrenal glands from those that originate in the testes. A DHEAS test may be ordered, along with other hormone tests, whenever excess (or more rarely deficient) androgen production is suspected and/or when your healthcare practitioner wants to evaluate your adrenal gland function.
ESTROGEN & ESTRADIOL
Estrogen is a group of hormones primarily responsible for the development of female sex organs and secondary sex characteristics. While estrogen is one of the major female sex hormones, small amounts are found in males.
There are three main estrogen fractions: estrone (E1), estradiol (E2), and estriol (E3). Estrone (E1) is the major estrogen after menopause. It is derived from metabolites from the adrenal gland and is often made in adipose tissue (fat). Estradiol (E2) is produced in women mainly in the ovary. In men, the testes and adrenal glands are the principal source of estradiol. In women, normal levels of estradiol provide for proper ovulation, conception, and pregnancy, in addition to promoting healthy bone structure and regulating cholesterol levels. Increased or decreased levels of estrogen are seen in many metabolic conditions. Beyond daily and cycle variations, illnesses such as hypertension (high blood pressure), anemia, and impaired liver and kidney function can affect estrogen levels in the body.
A protein produced by the liver and found in plasma. It is responsible, in part, for the clotting of blood. Plasma serves as the medium of exchange for vital minerals such as sodium and potassium, thus helping maintain a proper balance in the body, which is critical to cell function.
FSH (Follicle-Stimulating Hormone)
A natural hormone made by the pituitary gland in the brain. Control of FSH production is a complex system involving hormones produced by the gonads (ovaries or testes), the pituitary, and the hypothalamus. Both estradiol and progesterone help the pituitary control the amount of FSH produced. FSH also facilitates the ability of the ovary to respond to LH. At the time of menopause, the ovaries stop functioning and FSH levels rise. In men, FSH stimulates the testes to produce mature sperm and also promotes the production of androgen binding proteins. FSH levels are relatively constant in males after puberty.
GGT (Gamma-Glutamyl Transferase)
An enzyme found mainly in the liver, very sensitive to changes in liver function. It is normally present in low levels in the blood. When the liver is injured or obstructed, the GGT level rises. It is the most sensitive liver enzyme in detecting bile duct problems. A rise in GGT can occur even when there is no identifi able cause that is related to liver disease. Elevated levels may also be due to congestive heart failure, alcohol consumption, and use of many prescription and non-prescription drugs.
A type of serum protein. Globulins are found in plasma (the liquid component of blood) which include other clotting proteins. Plasma serves as the medium of exchange for vital minerals such as sodium and potassium, thus helping maintain a proper balance in the body, which is critical to cell function.
A type of sugar the body manufactures for energy from carbohydrates. Quantitative whole blood glucose tests are useful to test for or monitor diabetes and hypoglycemia.
A type of white blood cell filled with granules that digest microorganisms. Part of the immune system, there are several types of white blood cells. Granulocytes and macrophages protect against infection by surrounding and destroying invading bacteria and viruses, and lymphocytes aid in immune defense.
The percentage of blood volume composed of red blood cells.
A sulfur-containing amino acid that is normally present in very small amounts in all cells of the body. In healthy cells, homocysteine is quickly converted into other products. Vitamins B6, B12, and folate are necessary to metabolize homocysteine. People who are deficient in these vitamins may have increased levels of homocysteine. Testing HCYS helps to determine if you are at increased risk of a heart attack or stroke and to determine if you are folate-defi cient or B12-defi cient. Recent studies have suggested that people who have elevated homocysteine levels have a much greater risk of heart attack or stroke than those with average levels.
The hemoglobin count measures the ability of your red blood cells to carry oxygen. It is the gas transporting protein molecule that makes up 95% of a red cell. A normal hemoglobin count is 14-17 for men and 12-16 for women. Most people still feel well with a hemoglobin count as low as 10.
Hgb-A1C (A1c and Estimated Average Glucose)
The A1c test evaluates the average amount of glucose in the blood over the last 2 to 3 months.
IGF-1 (Insulin-Like Growth Factor – 1)
Also known as: Somatomedin C. Formal name: Insulinlike Growth Factor – 1. Related tests: Growth Hormone (GH), Glucose, Glucose Tolerance Test. Identifies diseases and conditions caused by deficiencies and overproduction of growth hormone (GH), to evaluate pituitary function.
As part of an evaluation of pituitary function; when you have symptoms of slow growth, short stature, and delayed development (in children) or decreased bone density, reduced muscle strength, and increased lipids (in adults) that suggest insufficient GH and IGF-1 production. Increased lipids in adults can lead to atherosclerosis.
A hormone that is produced and stored in the pancreas. Digested food breaks down into basic components such as glucose, a main source of energy for the body. Insulin is vital for the transportation and storage of glucose at the cellular level; it helps regulate blood glucose levels and has a role in lipid metabolism.
IRON (Serum Fe)
An essential mineral the body needs to make hemoglobin in red blood cells, which carry oxygen throughout the body. Iron is a critical part of hemoglobin, the protein in red blood cells that binds oxygen in the lungs and releases it as blood travels to other parts of the body. Low iron levels can lead to anemia, in which the body does not have enough red blood cells. Other conditions can cause too much iron to accumulate in your body. This can produce damage to several organs, including the liver, heart, and pancreas.
LDH (Lactate Dehydrogenase)
An enzyme found in almost all body tissues, but only a small amount of it is usually detectable in the blood. Contained within the tissues’ cells, LDH is released into the bloodstream when cells are damaged or destroyed. Because of this, the LDH test can be used as a general marker of injury to cells. Elevations of LDH may be measured either as a total LDH or as LDH isoenzymes. LDH is elevated in a wide variety of conditions, refl ecting its widespread tissue distribution. Historically, it has been used to help diagnose and monitor a heart attack.
Identifies patients who are at risk for heart attack and stroke associated with atherosclerosis, but do not have elevated LDL levels.
Lp (a)-Lipoprotein (a)
A lipoprotein, consisting of an LDL molecule attached to another protein, Apolipoprotein (a). Lp(a) may be an independent risk factor for heart disease; i.e., patients with acceptable lipid levels but elevated Lp(a) are still at risk for heart disease. In the body, Apolipoprotein (a) can interfere with the function of plasminogen (resulting in blood clot formation) and can help bind LDL molecules to artery walls (speeding up plaque formation and the narrowing and hardening of the arteries). It is this dual action that may explain the role of Lp(a) in the promotion of cardiovascular disease.
Lp(a) levels are genetically determined and will remain fairly constant in an individual over a lifetime; their levels are not affected by diet, exercise, and other typical lifestyle modifications used to lower lipid levels. Lp(a) is not currently routinely ordered. It may be ordered along with other lipid tests to selectively screen for risk factors for coronary artery disease (CAD) and cerebral vascular disease. Lp(a) and several other emerging cardiac risk markers (such as Apo B, hs-CRP, Apo A, and homocysteine levels) are ordered on patients who have a strong family history of premature coronary artery disease. Some healthcare practitioners may also order these tests on patients with existing heart or vascular disease, especially those who have normal or only mildly elevated lipids. Since about 50% of the people who have heart attacks have normal cholesterol levels, healthcare practitioners are starting to look at other factors that may have an influence on heart disease. It is thought that elevated Lp(a) levels can exacerbate other heart and vascular disease processes.
As the fourth most abundant mineral in the body, magnesium is essential to good health. The largest amount of magnesium is found in the bones (60%). Only one percent is found in the blood, but the body works very hard at keeping these levels constant. Magnesium is involved in more than 300 enzymatic reactions and therefore the systems in the body supported by having the right amount of magnesium present are many. Magnesium supplementation should be considered when the following conditions are present: High blood pressure, cardiovascular disease, heart attack, endothelial dysfunction, diabetes mellitus,osteoporosis, migraine headaches, asthma, and arteriosclerosis.
A mineral that is vital to normal body processes, which include nerve and muscle functioning. Too much sodium, however, can increase the chances of high blood pressure. Testing for sodium levels is performed to determine whether sodium concentration is within normal limits and to help evaluate electrolyte balance and kidney function. Test results generally help to identify dehydration or edema; and also to monitor certain chronic conditions, like high or low blood pressure.
In the body, phosphorus exists as a mineral; it is combined with oxygen to form a variety of phosphates (PO4). Phosphates are vital for energy production, muscle and nerve function, and bone growth. They also play an important role as a buffer, helping to maintain the body’s acidbase balance. Phosphorus testing is very important in people who are malnourished or who are being treated for ketoacidosis. Phosphorus testing is used to help diagnose and evaluate the severity of conditions and diseases that affect the gastrointestinal tract, interfering with the absorption of phosphorus, calcium, and magnesium. Testing also can help to diagnose disorders that affect the kidneys.
The platelet count measures your blood’s ability to clot. A normal platelet count is 150,000-300,000. Normal clotting is still possible with a platelet count of 100,000. Platelets (or thrombocytes) are very small cellular components of blood that help the clotting process by sticking to the lining of blood vessels. Platelets are made in the bone marrow and survive in the circulatory system for an average of 9–10 days before being removed from the body by the spleen. Recent research has shown that platelets help fight infections by releasing proteins that kill invading bacteria and some other microorganisms. In addition, platelets stimulate the immune system.
An electrolyte, a positively charged molecule that works with other electrolytes, such as sodium, chloride, and bicarbonate (total CO2) to help regulate the amount of fluid in the body, stimulate muscle contraction, and maintain a stable acid-base balance. Potassium is present in all body fluids, but mostly potassium is found within your cells. Because the blood concentration of potassium is so small, minor changes can have signifi cant consequences. If potassium levels go too low or too high, your health may be in considerable danger: you are at risk for developing shock, respiratory failure, or heart rhythm disturbances. An abnormal concentration can alter the function of neuromuscular tissue; for example, the heart muscle may lose its ability to contract.
A steroid hormone whose main role is to help prepare a woman’s body for pregnancy; it works in conjunction with several other female hormones. Increased progesterone levels also are seen occasionally with luteal ovarian cysts, molar pregnancies, and with a rare form of ovarian cancer. Increased levels are occasionally due to an overproduction of progesterone by the adrenal glands.
PSA (Prostate Specific Antigen)
A protein produced primarily by cells in the prostate, a small gland that encircles the urethra in males and produces a fluid that makes up part of semen. PSA exists in two forms in the blood: free (not bound) and complexed (bound to a protein). This test measures the amount of prostate specifi c antigen (PSA) in the blood. It was developed as a tumor marker to screen for and to monitor prostate cancer. Elevated levels of PSA are associated with prostate cancer and benign prostate hypertrophy, but levels tend to increase in all men as they age.
PT; PTT; INR (Prothrombin Time and International Normalized Ratio)
Prothrombin is one of the coagulation factors produced by the liver. The prothrombin time (PT) test measures how long it takes for a clot to form in a sample of blood. In the body, the clotting process involves a series of sequential chemical reactions called the coagulation cascade, in which coagulation or “clotting” factors are activated one after another and result in the formation of a clot.
To standardize results across the U.S. and the world, a World Health Organization (WHO) committee developed and recommended the use of the Internationalized Normalized Ratio (INR) with the PT test for patients who are receiving the blood-thinning medication warfarin (Coumadin). The INR is a calculation that adjusts for changes in the PT reagents and allows for results from different laboratories to be compared. Most laboratories are now reporting both PT and INR values whenever a PT test is performed. However, the INR should not be used to evaluate PT for patients who are not on blood-thinning medications. PTT is conducted to evaluate the function of all coagulation factors. RBC (Red blood cell count) – The most recognizable component of whole blood, red blood cells contain hemoglobin, a complex protein that carries oxygen throughout the body. Manufactured in the bone marrow, red blood cells are continuously being produced and broken down. They live for approximately 120 days in the circulatory system and are eventually removed by the spleen. Red cells normally make up 40-50% of the total blood volume. The red cells are produced continuously in our bone marrow from stem cells at a rate of about 2-3 million cells per second.
TESTOSTERONE FREE & TOTAL
Testosterone is a steroid hormone (androgen) produced by special endocrine tissue (the Leydig cells) in the male testes. Its production is stimulated and controlled by luteinizing hormone (LH), which is manufactured in the pituitary gland.
Testosterone is also produced by the adrenal glands in both males and females and, in small amounts, by the ovaries in females. In women, testosterone is converted to estradiol, the main sex hormone in females. Levels increase after exercise, but decrease with age. About two-thirds of testosterone circulates in the blood bound to sex-hormone binding protein and slightly less than one-third bound to albumin. A small percent (about 1-4%) circulates as free testosterone.
In females, testosterone testing may be done if a patient has irregular or no menstrual periods, is having diffi culty getting pregnant, or appears to have masculine features, such as facial and body hair, male pattern baldness, and a low voice. Testosterone levels can rise because of tumors that develop in either the ovary or adrenal gland or because of other conditions, such as polycystic ovarian syndrome (PCOS).
THYROID PANEL (TSH, T-3 TOTAL & FREE, T-4 TOTAL & FREE)
A group of tests that are often ordered together to help evaluate thyroid gland function and help diagnose thyroid disorders. The tests included in a thyroid panel measure the amount of thyroid hormones in your blood. These hormones are chemical substances that travel through the bloodstream and control or regulate your body’s metabolism – how it functions and uses energy.
The thyroid panel usually includes:
TSH (thyroid stimulating hormone or thyrotropin) – to test for hypothyroidism, hyperthyroidism andto monitor thyroid replacement therapy
T4 or free T4 (thyroxine) – to test for hypothyroidism and hyperthyroidism
T3 or free T3 (triiodothyronine) – to test for hyperthyroidism
TSH is produced by the pituitary gland and is part of the body’s feedback system to maintain stable amounts of the thyroid hormones T4 and T3 in the blood.
A chemical produced when the body breaks down substances called purines found in certain foods and drinks. Purines are chemicals that come from nucleic acids (DNA). Most uric acid is removed by the kidneys and disposed of in the urine; the remainder is excreted in the feces. The presence of excess uric acid can cause the condition called gout – an inflammation that occurs in joints when crystals derived from uric acid form in the joint fluid. The uric acid test is used to learn whether the body might be breaking down cells too quickly or not getting rid of uric acid quickly enough. Increased serum uric acid levels are linked to obesity, high blood pressure, and distorted cholesterol levels, all of which are also associated with increased risk for heart disease.
A fat soluble vitamin found in very few foods. Vitamin D comes from two sources: endogenous, which is produced in the skin on exposure to sunlight, and exogenous, which is ingested in foods and supplements. The main role of Vitamin D is to help regulate the absorption of calcium, phosphorus, and (to a lesser extent) magnesium. Vitamin D is vital for the growth and health of bone.
WBC (White Blood Cell Count)
White blood cells, or Leukocytes are responsible for protecting the body from invasion by foreign substances such as bacteria, fungi, and viruses. The white blood cell count measures your body’s ability to fight infection. A normal white blood cell count is 4,000- 9,000. A low white blood cell count may mean that you are more likely to get an infection. A high white blood cell count may indicate an infection, or it may be caused by a specific type of disease. The majority of white blood cells are produced in the bone marrow, where they outnumber red blood cells by two to one.