Glossary - Blood & Health Test & Other Medical Definitions


(We thought you might find these terms helpful to know...but might not have the time to "Google" them!)


Adrenal Cortex

The outer portion of the adrenal gland located on top of each kidney. The adrenal cortex produces steroid hormones which regulate carbohydrate and fat metabolism and mineralocorticoid hormones which regulate salt and water balance in the body.

Adrenal Gland

One of a pair of small glands, each of which sits on top of one of the kidneys. The adrenal is made up of an outer wall (the cortex) and an inner portion (the medulla).

The adrenal glands produce hormones that help control the heart rate, blood pressure, the way the body uses food, and other vital functions. The adrenal cortex secretes steroid (cortisone-related) hormones and mineralocortoids that regulate the levels of minerals such as sodium and potassium in the blood.

Amino Acid

One of the 20 building blocks of protein. The sequence of amino acids in a protein and, hence, the function of that protein are determined by the genetic code in the DNA.

Amino acids are molecules that (in technical terms) contain a basic amino (NH2) group, an acidic carboxyl (COOH) group and a side chain attached to an alpha carbon atom.

The 20 amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

The term “amino acids” dates to the middle of the 19th century. The idea that amino acids are “Bausteine” (building stones) came from the Nobel Prize winning German biochemist Albrecht Kossel (1853-1927).


An immunoglobulin, a specialized immune protein, produced because of the introduction of an antigen into the body, and which possesses the remarkable ability to combine with the very antigen that triggered its production.

The production of antibodies is a major function of the immune system and is carried out by a type of white blood cell called a B cell. Antibodies can be triggered by and directed at foreign proteins, microorganisms, or toxins. Some antibodies are auto antibodies and home in against our own tissues.

The term “antibody” dates to 1901. Prior to that time, an “antibody” referred to any of a host of different substances that served as “bodies” (foot soldiers) in the fight against infection and its ill effects.

Antinuclear Antibody (ANA)

Antinuclear antibody (ANA) is an unusual antibody directed against structures within the nucleus of the cell. ANAs are found in patients whose immune system is predisposed to cause inflammation against their own body tissues. Antibodies that are directed against one’s own tissues are referred to as auto antibodies. The propensity for the immune system to work against its own body is referred to as autoimmunity. ANAs indicate the possible presence of autoimmunity.

Blood Plasma

The liquid part of the blood and lymphatic fluid, which makes up about half of its volume. Plasma is devoid of cells and, unlike serum, has not clotted. Blood plasma contains antibodies and other proteins. It is taken from donors and made into medications for a variety of blood-related conditions. Some blood plasma is also used in non-medical products.

C-Reactive Protein (CRP)

A plasma protein that rises in the blood with the inflammation from certain conditions.

C-reactive protein is one of the plasma proteins known as acute-phase proteins: proteins whose plasma concentrations increase (or decrease) by 25% or more during inflammatory disorders.

C-reactive protein can rise as high as 1000-fold with inflammation. Conditions that commonly lead to marked changes in CRP include infection, trauma, surgery, burns, inflammatory conditions, and advanced cancer. Moderate changes occur after strenuous exercise, heatstroke, and childbirth. Small changes occur after psychological stress and in several psychiatric illnesses.

C-reactive protein is therefore a test of value in medicine, reflecting the presence and intensity of inflammation, although an elevation in C-reactive protein is not the telltale diagnostic sign of any one condition.

Since inflammation is believed to play a role in the development of coronary artery disease, markers of inflammation have been tested in respect to heart health. C-reactive protein was found to be the only marker of inflammation that independently predicts the risk of a heart attack. (N Engl J Med 2000;342:836-43.) C-reactive protein test may therefore be added to the screening battery of cholesterol and other lipid tests to detect people at risk for a heart attack.


Mainly sugars and starches, together constituting one of the three principal types of nutrients used as energy sources (calories) by the body. Carbohydrates can also be defined chemically as neutral compounds of carbon, hydrogen and oxygen.

Carbohydrates come in simple forms such as sugars and in complex forms such as starches and fiber. The body breaks down most sugars and starches into glucose, a simple sugar that the body can use to feed its cells. Complex carbohydrates are derived from plants (e.g., “vegetables”). Dietary intake of complex carbohydrates can lower blood cholesterol when they are substituted for saturated fat.


The most common type of steroid in the body, cholesterol has gotten something of a bad name. However, cholesterol is a critically important molecule. It is essential to the formation of:

  • Bile acids (which aid in the digestion of fats)
  • Vitamin D
  • Progesterone
  • Estrogens (estradiol, estrone, estriol)
  • Androgens (androsterone, testosterone)
  • Mineralocorticoid hormones (aldosterone, corticosterone) and
  • Glucocorticoid hormones (cortisol).
  • Cholesterol is also necessary to the normal permeability and function of cell membranes, the membranes that surround cells.

Cholesterol is carried in the bloodstream as lipoproteins. Low-density lipoprotein (LDL) cholesterol is the “bad” cholesterol because elevated LDL levels are associated with an increased risk of coronary artery (heart) disease. Conversely, high-density lipoprotein (HDL) cholesterol is the “good” cholesterol since high HDL levels are associated with less coronary disease.

After the age of 20, cholesterol testing is recommended every 5 years.

A diet high in saturated fats tends to increase the blood cholesterol levels while diets high in unsaturated fats tend to do the opposite, to lower blood cholesterol levels.

Although some cholesterol is obtained from the diet, most cholesterol is made in the liver and other tissues. The treatment of elevated cholesterol therefore involves not only diet but also weight loss and regular exercise (and, occasionally, medications).


An adrenocorticoid hormone, a naturally occurring hormone made by and secreted by the adrenal cortex, the outer part (the cortex) of the adrenal gland.

Cortisone was the first of the “miracle drugs” for the treatment of rheumatoid arthritis. This historic feat was achieved by Edward C Kendall and Philip S. Hench at the Mayo Clinic in Rochester, Minnesota. Their discovery stemmed from the astute clinical observation that a woman with severe rheumatoid arthritis felt much better during pregnancy. They found what was responsible. It was a hormone from the outer part (the cortex) of the adrenal glands. They called it “cortisone.” On Sept. 21, 1948, Hench gave a synthesized version of cortisone developed by Kendall to a patient with arthritis. Kendall and Hench shared the Nobel Prize in Physiology or Medicine in 1950 with Tadeus Reichstein from Switzerland “for their discoveries relating to the hormones of the adrenal cortex, their structure, and biological effects.”

Synthetic cortisone acts after it is converted by the body (metabolized) to cortisol to exert its powerful anti-inflammatory (and other) effects. Its many uses include the treatment of adrenocortical deficiency and conditions associated with inflammation.


DNA is one of two types of molecules that encode genetic information. (The other is RNA.) In humans, DNA is the genetic material; RNA is transcribed from it. In some other organisms, RNA is the genetic material and, in reverse fashion, the DNA is transcribed from it.)

DNA is a double-stranded molecule held together by weak hydrogen bonds between base pairs of nucleotides. The molecule forms a double helix in which two strands of DNA spiral about one other. The double helix looks something like an immensely long ladder twisted into a helix, or coil. The sides of the “ladder” are formed by a backbone of sugar and phosphate molecules, and the “rungs” consist of nucleotide bases joined weakly in the middle by the hydrogen bonds.

There are four nucleotides in DNA. Each nucleotide contains a base: adenine (A), guanine (G), cytosine (C), or thymine (T). Base pairs form naturally only between A and T and between G and C so the base sequence of each single strand of DNA can be simply deduced from that of its partner strand.

The genetic code in DNA is in triplets such as ATG. The base sequence of that triplet in the partner strand is therefore TAC.

The first proof that DNA was the hereditary material was provided in 1944 by Oswald Avery, Maclyn McCarty and Colin MacLoed. The double helical structure of DNA was discovered in 1953 by James D. Watson and Francis H.C. Crick with the invaluable collaboration of the X-ray crystallographer Rosalind Franklin. Watson and Crick shared the 1962 Nobel Prize in Physiology or Medicine with Maurice H.F. Wilkins.

ESR (Sedimentation Rate)

A blood test that detects and monitors inflammation in the body. It measures the rate at which red blood cells (RBCs) in a test tube separate from blood serum over time, becoming sediment in the bottom of the test tube. The sedimentation rate increases with more inflammation. Also called the erythrocyte sedimentation rate. Abbreviated as “sed” rate or ESR.

Genetic Code

The instructions in a gene that tell the cell how to make a specific protein. A, T, G, and C are the “letters” of the DNA code. They stand for the chemicals adenine, thymine, guanine, and cytosine, respectively, that make up the nucleotide bases of DNA. Each gene’s code combines the four chemicals in various ways to spell out 3-letter “words” that specify which amino acid is needed at every step in making a protein.

The discovery of the genetic code clearly ranks as one of the premiere events in what has been called the Golden Age of Biology and Medicine.


1. A group of cells that secrete a substance for use in the body. For example, the thyroid gland.

2. A group of cells that removes materials from the circulation. For example, a lymph gland.


Glucose is a simple sugar (monosaccharide) that is used to increase the level of blood glucose when the level falls too low (hypoglycemia). Glucose is a glucose-elevating agent. Other glucose-elevating agents are diazoxide (Proglycem) and glucagon.

Glucose is the primary fuel used by most cells in the body to generate the energy that is needed to carry out cellular functions. When glucose levels fall to hypoglycemic levels, cells cannot function normally, and symptoms develop such as nervousness, cool skin, headache, confusion, convulsions or coma. Ingested glucose is absorbed directly into the blood from the intestine and results in a rapid increase in the blood glucose level.

Glucose Tolerance

How is diabetes mellitus diagnosed?

The fasting plasma glucose test is the preferred way to diagnose diabetes. It is easy to perform and convenient. After the person has fasted overnight (at least 8 hours), a single sample of blood is drawn and sent to the laboratory for analysis.

Normal fasting plasma glucose levels are less than 110 milligrams per deciliter (mg/dl). Fasting plasma glucose levels of more than 126 mg/dl on two or more tests on different days indicate diabetes. If the overnight fasting blood glucose is greater than 126 mg/dl on two different tests on different days, the diagnosis of diabetes mellitus is made.

A random blood glucose test can also be used to diagnose diabetes. Random blood samples (if taken shortly after eating or drinking) may be used to test for diabetes when symptoms are present. A blood glucose level of 300 mg/dl or higher indicates diabetes, but it must be reconfirmed on another day with a fasting plasma glucose or an oral glucose tolerance test.

What is the oral glucose tolerance test?

With an oral glucose tolerance test, the person fasts overnight (at least 8 but not more than 16 hours). Then first, the fasting plasma glucose is tested. After this test, the person receives 75 grams of glucose (100 grams for pregnant women). Usually, the glucose is in a sweet-tasting liquid that the person drinks. Blood samples are taken up to four times to measure the blood glucose.

For the test to give reliable results, the person must be in good health (not have any other illnesses, not even a cold). Also, the person should be normally active (not lying down, for example, as an inpatient in a hospital) and should not be taking medicines that could affect the blood glucose. For 3 days before the test, the person should have eaten a diet high in carbohydrates (150- 300 grams per day). The morning of the test, the person should not smoke or drink coffee.

The classic oral glucose tolerance test measures blood glucose levels 5 times over a period of 3 hours. Some physicians simply get a baseline blood sample followed by a sample 2 hours after drinking the glucose solution. In a person without diabetes, the glucose levels rise and then fall quickly. In someone with diabetes, glucose levels rise higher than normal and fail to come back down as fast.

People with glucose levels between normal and diabetic have impaired glucose tolerance (IGT). People with IGT do not have diabetes. Each year, only 1-5% of people whose test results show IGT actually develop diabetes. Weight loss and exercise may help people with IGT return their glucose levels to normal. Recent studies have shown that IGT itself may be a risk factor for the development of heart disease, and whether IGT turns out to be an entity that deserves treatment itself is something that physicians are currently debating.

What may the results of the oral glucose tolerance test indicate?

Glucose tolerance tests may lead to one of the following diagnoses:

Normal response: A person is said to have a normal response when the 2-hour glucose level is less than 140 mg/dl, and all values between 0 and 2 hours are less than 300 mg/dl.

Impaired glucose tolerance: A person is said to have IGT when the fasting plasma glucose is less than 126 mg/dl and the 2-hour glucose level is between 140 and 199 mg/dl.

Diabetes: A person has diabetes when two diagnostic tests done on different days show that the blood glucose level is high.

Gestational diabetes: A woman has gestational diabetes when she has any two of the following: a fasting plasma glucose of more than 105 mg/dl, a 1-hour glucose level of more than 190 mg/dl, a 2-hour glucose level of more than 165 mg/dl, or a 3-hour glucose level of more than 145 mg/dl.

HDL Cholesterol

Lipoproteins, which are combinations of lipids (fats) and proteins, are the form in which lipids are transported in the blood. The high-density lipoproteins transport cholesterol from the tissues of the body to the liver so it can be gotten rid of (in the bile). HDL cholesterol is therefore considered the “good” cholesterol. The higher the HDL cholesterol level, the lower the risk of coronary artery disease.

Even small increases in HDL cholesterol reduce the frequency of heart attacks. For each 1 mg/dl increase in HDL cholesterol there is a 2 to 4% reduction in the risk of coronary heart disease. Although there are no formal guidelines, proposed treatment goals for patients with low HDL cholesterol are to increase HDL cholesterol to above 35 mg/dl in men and 45 mg/dl in women with a family history of coronary heart disease; and to increase HDL cholesterol to approach 45 mg/dl in men and 55 mg/dl in women with known coronary heart disease.

The first step in increasing HDL cholesterol levels is life style modification. Regular aerobic exercise, loss of excess weight (fat), and cessation of cigarette smoking cigarettes will increase HDL cholesterol levels. Moderate alcohol consumption (such as one drink a day) also raises HDL cholesterol When life style modifications are insufficient, medications are used. Medications that are effective in increasing HDL cholesterol include nicotinic acid (niacin), gemfibrozil (Lopid), estrogen, and to a lesser extent, the statin drugs.


In 1981, homosexual men with symptoms that now are considered diagnostic of AIDS were first described in Los Angeles and New York. The men had an unusual type of lung infection (pneumonia) called Pneumocystis carinii pneumonia (PCP) and rare skin tumors called Kaposi’s sarcoma. The patients were noted to have severe suppression of a specific type of immune blood cells, called CD4 cells. These cells, often referred to as T cells, help the body fight infections. Shortly thereafter, this disease was recognized throughout the United States, Western Europe, and Africa. In 1983, researchers in the United States and France described the virus that causes AIDS, now known as HIV. In 1985, a blood test became available that measures antibodies to HIV, which thereby detects the body’s immune response to the HIV. This blood test remains the best method for diagnosing HIV infection. Recently, tests have become available to look for these same antibodies in the saliva and urine.

How is HIV spread (transmitted)?

HIV is present in the blood and genital secretions of virtually all infected individuals, regardless of whether or not they have symptoms. The spread of HIV can occur when these secretions come in contact with tissues such as those lining the vagina, anal area, mouth, or eyes (the mucosal membranes), or with a break in the skin, such as from a cut or puncture by a needle. The most common ways in which HIV is spreading throughout the world include sexual contact, needle sharing, and transmission from infected mothers to their newborns during pregnancy, labor (the delivery process), or breast- feeding.


An amino acid produced by the body, usually as a byproduct of consuming meat. Homocysteine is made from another amino acid, methionine, and then in turn is converted into other amino acids.

Elevated levels of homocysteine in the blood appear to make for an elevated risk of cardiovascular (heart and vessel) disease. Levels of homocysteine as low as 12 micromoles per liter of blood plasma have been found associated with an increased risk of heart attack, stroke, peripheral vascular disease and venous thromboembolism (blood clots in the veins). A homocysteine level of 15 micromoles or above has a heart attack rate three times as high as normal. Even a level of 12 micromoles can double the coronary risk.

Homocysteine can damage blood vessels in several ways. It injures the cells that line arteries and stimulates the growth of smooth muscle cells. Homocysteine can also disrupt normal blood clotting mechanisms, increasing the risk of clots that can bring on a heart attack or stroke.

Elevated levels of homocysteine also appear to increase the chance of Alzheimer’s disease. In a remarkable study published in The New England Journal of Medicine in 2002, a large contingent of elderly people free of dementia were studied prospectively (in a forward-looking way). The results were quite startling. An elevated blood plasma level of the amino acid homocysteine was found to be an independent predictor of the development of clinical dementia, usually due to Alzheimer’s disease. The higher the homocysteine level, the more likely a person was to later develop Alzheimer’s. When plasma homocysteine is at a high level (over 14 micromoles per liter of blood), the risk of Alzheimer’s disease doubled. The strength of this association is very powerful.

The ways to bring down homocysteine are by eating less meat and by taking supplements of the B vitamins folic acid, B6, and B12 that are needed by the enzymes that process homocysteine. (Homocysteine builds up when the amino acid methionine cannot be converted to cysteine because an enzyme is lacking or is present in inadequate amounts. The B vitamins folic acid (folate), B6, and B12 are crucial to these conversion enzymes.)

Since folic acid supplementation can reduce plasma homocysteine levels, a possible strategy to help prevent both heart disease and Alzheimer’s may be to provide more folic acid.

Concern for homocysteine as a cardiovascular risk factor came first. It dates to 1969 when Dr. Kilmer S. McCully reported that children born with a genetic error of metabolism called homocystinuria that causes the homocysteine levels to be very high sometimes died at a very young age with advanced disease in their arteries. However, until the 1990′s the importance of homocysteine in cardiovascular disease was overshadowed by cholesterol story.


A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.

Many hormones are secreted by specialized glands such as the thyroid gland. Hormones are essential for every activity of daily living, including the processes of digestion, metabolism, growth, reproduction, and mood control. Many hormones, such as the neurotransmitters, are active in more than one physical process.


Hypoglycemia means low blood sugar (glucose). The blood glucose levels in healthy individuals fluctuate depending greatly on the duration of fasting. The normal range is 70 to 120 mg/dl after an overnight (12 hours) fast. In healthy men, the blood glucose can drop to 55 mg/dl after 24 hours of fasting and to 48 mg/dl after 72 hours of fasting. In healthy women, glucose levels can be as low as 35 mg/dl after only 24 hours of fasting.

Since blood glucose levels can fluctuate widely in healthy subjects, and symptoms of hypoglycemia can be vague and nonspecific, establishing the diagnosis of hypoglycemia as the cause of symptoms is often difficult. When symptoms of hypoglycemia occur together with a documented blood glucose under 45 mg/dl, and the symptoms promptly resolve with the administration of glucose, the diagnosis can be made with more certainty.

Immune System

A complex system that is responsible for distinguishing us from everything foreign to us, and for protecting our body against infections and foreign substances. The immune system works to seek and kill invaders of our body.


One of a pair of organs located in the right and left side of the abdomen which clear “poisons” from the blood, regulate acid concentration and maintain water balance in the body by excreting urine. The kidneys are part of the urinary tract. The urine then passes through connecting tubes called “ureters” into the bladder. The bladder stores the urine until it is released during urination.

LDL Cholesterol

A molecule that is a combination of lipid (fat) and protein. Lipoproteins are the form in which lipids are transported in the blood.

Low-density lipoprotein (LDL) transports cholesterol from the liver to the tissues of the body. LDL cholesterol is therefore considered the “bad” cholesterol.


Another word for “fat” or “fats” (Please see the various meanings of Fat.) Lipids can be more formally defined as substances such as a fat, oil or wax that dissolves in alcohol but not in water. Lipids contain carbon, hydrogen and oxygen but have far less oxygen proportionally than carbohydrates.

Lipids are an important part of living cells. Together with carbohydrates and proteins, lipids are the main constituents of plant and animal cells.

Cholesterol and triglycerides are lipids. Lipids are easily stored in the body. They serve as a source of fuel and are an important constituent of the structure of cells.

Lipids include fatty acids, neutral fats, waxes and steroids (like cortisone). Compound lipids (lipids complexed with another type of chemical compound) comprise the lipoproteins, glycolipids and phospholipids.

Etymology: Whereas the everyday term “fat” comes from the Old English (from “faett” meaning crammed or adorned), the more scientific term “lipid” comes from the Greek “lipos” which referred to animal fat or vegetable oil. The derivation of a biomedical term from another tongue such as Greek, Latin or French lends it a certain “je ne sais quoi” (something that cannot be easily expressed), a touch of continental class.


A solid organ located in the right upper quadrant of the abdomen. The liver plays a major role in metabolism, digestion, detoxification and elimination of substances from the body. The liver removes waste products and worn-out cells from the blood. The liver is the largest solid organ in the body. The liver weighs about three and a half pounds (1.6 kilograms). It measures about 8 inches (20 cm) horizontally (across) and 6.5 inches (17 cm) vertically (down) and is 4.5 inches (12 cm) thick.

Test Includes:

  • Albumin
  • Alkaline Phosphatase
  • Bilirubin, Total & Direct
  • Protein, Total
  • ALT (SGPT)
  • AST (SGOT)

An almost colorless fluid that travels through vessels called lymphatics in the lymphatic system and carries cells that help fight infection and disease.


The whole range of biochemical processes that occur within us (or any living organism). Metabolism consists both of anabolism and catabolism (the buildup and breakdown of substances, respectively). The term is commonly used to refer specifically to the breakdown of food and its transformation into energy.

Prostate Cancer

An uncontrolled (malignant) growth of cells in the prostate gland which is located at the base of the urinary bladder and is responsible for helping control urination as well as forming part of the semen. Prostate cancer is the second leading cause of death of males in the U.S.

 Prostate Specific Antigen (PSA)

A test used to screen for cancer of the prostate and to monitor treatment.

PSA is a protein produced by the prostate gland. Although most PSA is carried out of the body in semen, a very small amount escapes into the blood stream. The PSA test is done on blood. Since the amount of PSA in blood is normally minute, the PSA test requires a very sensitive method based on monoclonal antibody technology. PSA in blood can be by itself as free PSA or it can join with other substances in the blood as bound PSA. Total PSA is the sum of free and bound forms. This is what is measured as the standard PSA test.

The PSA value used most frequently as the highest normal level is 4 ng/mL (nanograms per milliliter). However, since the prostate gland generally increases in size and produces more PSA with increasing age, it is normal to have lower levels in young men and higher levels in older men. Age-specific PSA levels are as follows (age group, upper normal): (40 – 49, 2.5), (50 – 59, 3.5), (60 – 69, 4.5), (70 – 79, 6.5). The use of age-specific PSA ranges for the detection of prostate cancer is controversial. Not all studies have agreed that this is better than simply using a level of 4 ng/mL as the highest normal value.

The PSA test is used in two distinctly different ways with respect to prostate cancer. It can be used in men who are not known to have the disease as a screening test and it can be used in men known to have the disease as a tumor marker or monitoring test:

Screening test: An abnormal result usually requires additional testing. Levels above 4 ng/mL but less than 10 ng/mL are suspicious. However, most men who have this level of abnormality will actually not have prostate cancer. As levels increase above 10 ng/mL, the probability of prostate cancer increases dramatically.

Monitoring test: An abnormal result following therapy indicates recurrence of prostate cancer.

PSA is not specific to prostate cancer. Other diseases can cause an elevated PSA. The most frequent is benign prostatic hypertrophy (BPH), an increase in the size of the prostate that typically occurs with aging. Infection of the prostate gland is another relatively common cause of an elevated PSA. Other conditions that can increase PSA include ischemia or infarction, urethral instrumentation, and urinary retention, and prostate biopsy.

The PSA test has other limitations. A small proportion of prostate cancers do not produce a detectable increase in blood PSA, even with advanced disease. Many early cancers will also not produce enough PSA to cause a significantly abnormal blood level. It is therefore important not to rely only on blood PSA testing. You should be aware that the most useful additional test is a physical prostate exam known as the digital rectal exam (DRE). Following a PSA test, this additional test is highly recommended by most doctors.


Proteins contain different amino acids that are linked together. Proteins are the molecules in the cell that “do things” – they are the machinery of the cell. Proteins can do things like catalyze reactions, provide locomotion and facilitate cell division.

Nutritionally, proteins provide both calories and the amino acid building blocks that are necessary for proper growth.


A type of cancer that starts in bone or connective tissue. The first sign of sarcoma is usually a soft, painless swelling in the affected area. Most sarcomas are fast- growing. Different types of cells may be found in a sarcoma, and the type of cell (i.e., spindle cell, clear cell, osteoblast) may be used to describe the cancer.

T4 Hormone

Thyroxine, a thyroid hormone.


A “male hormone” — a sex hormone produced by the testes that encourages the development of male sexual characteristics, stimulates the activity of the male secondary sex characteristics, and prevents changes in them following castration. Chemically, testosterone is 17-beta-hydroxy-4-androstene-3-one.

Testosterone is the most potent of the naturally occurring androgens. The androgens cause the development of male sex characteristics, such as a deep voice and a beard; they also strengthen muscle tone and bone mass.

High levels of testosterone appear to promote good health in men, for example, lowering the risks of high blood pressure and heart attack. High testosterone levels also correlate with risky behavior, however, including increased aggressiveness and smoking, which may cancel out these health benefits.

Testosterone may be given to treat medical conditions, including female (but not male) breast cancer, hypogonadism (low gonadal function) in the male, cryptorchism (nondescent of the testis into the scrotum), and menorrhagia (irregular periods).


An adjective and a noun, pertaining to the thyroid gland or, less often today, to a preparation made of mammalian thyroid tissue to treat hypothyroidism. For example, the sentence “My thyroid is not making enough thyroid hormone” uses “thyroid” (redundantly) as both an adjective and noun.

The thyroid is located in the lower part of the neck below the Adam’s apple. It is wrapped around the windpipe (the trachea) and has the shape of a butterfly, since it is formed by two wings (lobes) which are attached by a middle part.


One of a number of poisons produced by certain plants, animals, and bacteria.

The term “toxin” is frequently used to refer specifically to a particular protein produced by some higher plants, animals and pathogenic (disease-causing) bacteria. A toxin typically has a high molecular weight (as compared to a simple chemical poison), is antigenic (elicits an antibody response), and is highly poisonous to living creatures.

The word “toxin” comes from the Greek “toxikon” = arrow poison and was introduced to medicine in 1888 by the Berlin physician Ludwig Brieger (1849-1909) as a name for poisons made by infectious agents.


The major form of fat. A triglyceride consists of three molecules of fatty acid combined with a molecule of the alcohol glycerol. Triglycerides serve as the backbone of many types of lipids (fats). Triglycerides come from the food we eat as well as from being produced by the body.

Triglyceride levels are influenced by recent fat and alcohol intake, and should be measured after fasting for at least 12 hours. A period of abstinence from alcohol is advised before testing for triglycerides.

Triglyceride levels do not provide clinically significant data about the risk of coronary artery disease beyond the information provided by serum cholesterol subfractions (HDL- and LDL-cholesterol).

Markedly high triglyceride levels (greater than 500mg/dl) can cause inflammation of the pancreas (pancreatitis). Therefore, these high levels should be treated aggressively with low fat diets and medications, if needed.

The word “triglyceride” reflects the fact that a triglyceride consists of three (“tri-”) molecules of fatty acid combined with a molecule of the alcohol glycerol (“-glyceride”) that serves as the backbone in many types of lipids (fats).


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