Glossary of Diabetes - G

G

Galactose

a simple sugar which does not participate in the glucose metabolism control system. It is half of the disaccharide, lactose (milk sugar).

Gangrene

Infection of dead body tissue. It is most often caused by a loss of blood flow, especially in the legs and feet. Gangrene is particularly dangerous in that the infection cannot be reached by body defense systems and so can proceed without interference.

Gastroparesis

A form of nerve damage that affects the stomach and intestines. Food is not digested properly and does not move through in a normal way, resulting in vomiting, nausea, or bloating. It often interferes with diabetes management. See also: Autonomic neuropathy.

Gene

a unit of heredity. Eye color is a particularly simple system. There are blue eye genes and brown eye genes and one's eyes are brown if one of the two eye color genes is a brown one and blue if blue genes are inherited from both parents. Each gene is a segment of DNA and is often controlled by other genes. In the case of glucose absorption, the gene whose expressed protein opens the glucose ports in the cell wall is normally inhibited by another gene's product. We have finally come to understand the normal process in considerable detail; it is the same in nematode worms, fish, mice, pigs, cows, and people.

Genetic

See also: heredity.

Gestation

pregnancy and birth

Gestational diabetes mellitus (GDM)

A type of diabetes mellitus that can occur when a woman is pregnant. During the pregnancy (usually later in it), the woman may have glucose (sugar) in her blood at a higher than normal level. However, when the pregnancy ends, the blood glucose levels return to normal in about 95 percent of all cases. It MUST be treated carefully by a physician for it is dangerous to both mother and child. If treated properly, there are usually no lasting effects on either. Women who have had an episode of GDM are at higher risk of developing Type 2 diabetes later on.

Gingivitis

infection of the gums, often chronic and low grade.

Gland

a tissue which produces a product used elsewhere. The pancreas is a large gland, and a complex one. It produces considerable quantities of bile acids for use in the intestines; these are carried to the intestines via ducts and so the pancreas is a ducted gland. Parts of the pancreas (chiefly the Islets of Langerhans) produce very small amounts of chemicals which are released directly into the blood; the pancreas is also therefore a ductless gland as well. These later substances are hormones, and so the pancreas is also an endocrine gland.

Glaucoma

an increase in the internal pressure in the eye. It is usually caused by a reduction in the outflow of fluid. Sufficiently high and prolonged glaucoma causes reduced vision by preventing perfusion of the retina, and can lead to blindness.

Gliclazide

A pill taken to lower the level of glucose (sugar) in the blood. Only some people with noninsulin-dependent diabetes take these pills. See also: Oral hypoglycemic agents. One of the sulfonylureas. (Diamicron)

Glimepiride

A pill taken to lower the level of glucose (sugar) in the blood. Only some people with noninsulin-dependent diabetes take these pills. See also: Oral hypoglycemic agents. One of the sulfonylureas. (Amaryl)

Glipizide

A pill taken to lower the level of glucose (sugar) in the blood. Only some people with noninsulin-dependent diabetes take these pills. See also: Oral hypoglycemic agents. One of the sulfonylureas. (Glucotrol)

Glomerular filtration rate

A measure of the kidneys' ability to filter blood as part of the waste removal process.

Glomeruli

Network of tiny blood vessels in the kidneys where the blood is filtered and waste products are removed.

Glucagon

A hormone that raises the level of glucose (sugar) in the blood by forcing the liver to release some of its intracellular stores of glucose.

Glucose

a simple sugar which is the chief carbohydrate fuel in food. In the dextrose form isomer, it is the chief product of photosynthesis in plants.

Glucose tolerance test

A test to see if a person has diabetes. The test is usually given in a lab or doctor's office in the morning before the person has eaten. A first sample of blood is taken from the person. Then the person drinks a liquid that has a measured amount of glucose in it (typically 75 grams). After one hour, a second blood sample is drawn, and, after another hour, a third sample is taken. The object is to see how well the body deals with the glucose in the blood over time without interference from other foods. Depending on the local lab, the number and spacing of samples may vary.

Glyburide, also called Glibenclamide

A pill taken to lower the level of glucose (sugar) in the blood. Only some people with noninsulin-dependent diabetes take these pills. See also: Oral hypoglycemic agents. One of the sulfonylureas. (Diabeta; Glynase; Micronase; Euglucon)

Glycemic index

The effect of a food on blood glucose (sugar) levels over a period of time. Researchers have discovered that some kinds of foods raise blood glucose levels more quickly than other foods containing the same amount of carbohydrates, at least under laboratory conditions. Cooked carrots get glucose into the blood faster than pure glucose! In practice, foods are not eaten alone and the presence of other foods changes the measured results for the pure food. In addition, some foods don't have much carbohydrate even if they get it into the blood quickly. A better guide is glycemic density which combines the glycemic index with the amount of carbohydrate in the food.

Glycogen

A substance made from multiple glucose molecules. Sometimes called 'animal starch'. It is stored in liver and muscle cells and can be converted to glucose when needed. The glucose in liver glycogen is put back into the blood when required. That in muscle cells is not, as they lack the necessary enzymatic machinery to export glucose into the blood.

Glycogenesis

The process by which glycogen is formed from glucose. Controlled by insulin. See also: Glycogen.

Glycosuria

Having glucose (sugar) in the urine. This means that the renal threshold for glucose has been exceeded in the blood which is clear evidence of too high levels as the kidneys are ordinarily excellent at conserving glucose. For most kidneys, this is about 200 mg/dl.

Glycosylated hemoglobin test

A blood test that measures the level of a particular variety of hemoglobin (HbA1c) which is itself a measure of a person's average blood glucose level for the 3-month period before the test. Glucose reacts with proteins throughout the body; indeed, this is thought to be one, if not the primary, mechanism by which high glucose levels cause damage (see Malliot reaction in cooking for a parallel). One of those reactions with hemoglobin is irreversible and relatively easily detected. Its concentration is an index of the average blood glucose level throughout the life of the red blood cell (about 90 days in most cases). See: Hemoglobin A1C.