Glossary: Diabetes

Content provided by the Faculty of the Harvard Medical School

Glossary

alpha cells: Cells that secrete the hormone glucagon; located in the islets of Langerhans of the pancreas.

autonomic neuropathy: Nerve damage that affects the autonomic nervous system, which controls digestive, bladder, bowel, cardiac, and sexual function.

beta cells: Cells that make and secrete insulin; located in the islets of Langerhans of the pancreas.

cataract: An increased thickening and clouding of the lens of the eye that can lead to vision loss.

diabetic ketoacidosis: A dangerous condition in which the blood becomes acidic due to a buildup of ketones; it arises during severe insulin deficiency.

diabetic retinopathy: A degenerative eye disorder in which small blood vessels in the retina initially leak and subsequently become blocked. Very fragile new vessels develop, but they ultimately bleed and cause scarring.

fasting plasma glucose test: A blood test that determines the amount of glucose in the blood after an overnight fast of at least eight hours; a measure at or above 126 mg/dL indicates diabetes.

gestational diabetes mellitus: A form of diabetes that has its onset during pregnancy, usually in the last trimester.

glaucoma: A disorder characterized by excessive fluid pressure within the eyeball; can occur as a complication of diabetes.

glucagon: A hormone produced by the alpha cells of the pancreas that increases the concentration of glucose in the blood.

glucose: A six-carbon sugar that serves as a main source of fuel for our bodies.

glycosylated hemoglobin test: A blood test that reflects average blood sugar levels over the preceding two to three months by measuring the amount of glucose adhering to hemoglobin, a protein in red blood cells. The product formed by the attachment of glucose to hemoglobin is known as HbA1c.

hyperglycemia: An abnormally high level of glucose in the blood.

hypoglycemia: A condition in which the blood sugar drops to an abnormally low level.

impaired fasting glucose: A condition diagnosed with a fasting glucose test; blood glucose levels are higher than normal but not yet diabetic.

impaired glucose tolerance: A condition similar to impaired fasting glucose (see previous entry), but diagnosed with an oral glucose tolerance test.

insulin: An anabolic (growth-promoting) hormone produced by the beta cells in the pancreas; it directs the passage of glucose, amino acids, and fatty acids into cells and promotes their storage.

insulin resistance: A reduced sensitivity to insulin's action; underlies type 2 diabetes and can contribute to hyperglycemia.

islets of Langerhans: Clusters of hormone-producing cells, including alpha and beta cells, that appear throughout the pancreas.

ketones: By-products of fat metabolism.

lactic acidosis: Rare but potentially lethal condition in which blood lactic acid levels increase.

oral glucose tolerance test: A two-part test that first measures blood glucose levels after an overnight fast, and then two hours after consumption of a sugary solution; sometimes used in conjunction with fasting plasma glucose test.

pancreas: An elongated gland that produces digestive enzymes and manufactures hormones, including insulin and glucagon, which are central to the metabolism of sugar, fat, and protein.

peripheral neuropathy: Damage to the long nerves radiating from the spine to the arms and legs.

peripheral vascular disease: A disorder caused by the blockage of blood vessels to the brain and extremities.

pre-diabetes: A condition in which a fasting plasma glucose test and/or an oral glucose tolerance test provide readings that are elevated, but not quite diabetic; raises the risk of diabetes.

Last updated:	January 23, 2007