Health

bisphosphonates: A class of compounds, including alendronate and risedronate, that slow bone resorption. These medications are used to prevent and treat osteoporosis.

bone mass: The total amount of bone tissue in the body.

bone mineral density (BMD): The amount of mineralized bone tissue in a given area, usually calculated in grams per square centimeter.

calcium: A mineral that is the primary component of hydroxyapatite. It is also vital to many physical processes, including heart rate, blood pressure, muscle contractions, the transmission of nerve signals, and the regulation of internal organs.

compact bone: Very dense bone tissue that forms the outer shell of bones and composes a large part of the long bones of the arms, legs, and ribs. Also called cortical bone or lamellar bone.

compression fracture: The collapse of a bone, most often a vertebra.

dorsal kyphosis: An abnormal front-to-back curvature of the mid-to-upper spine that can result from compression fractures of vertebrae. Commonly called dowager's hump.

dual energy x-ray absorptiometry (DXA): A test in which x-rays are used to measure bone density and produce an image of the bone; the preferred screening test for osteoporosis.

glucocorticoids: A class of hormones produced by the adrenal gland and simulated by medications such as prednisone. These medications can contribute to osteoporosis.

hormone therapy: Augmentation of a woman's depleted hormones with estrogen alone or a combination of estrogen and progestin or progesterone; a measure to reduce osteoporosis risk in postmenopausal women.

hydroxyapatite: The mature, hard, somewhat crystalline mineral compounds in bone tissue.

hyperparathyroidism: A condition in which the body produces excessive amounts of parathyroid hormone (PTH), disrupting the regulation of calcium. As a result, calcium is taken from the bones, blood levels of calcium rise, and increased amounts of calcium may be excreted in urine.

osteoblasts: Bone-forming cells.

osteoclasts: Bone-removing cells.

osteocytes: Osteoblasts that have completed their bone-forming function and have become trapped in new bone tissue, evolving into structural bone cells.

osteons: The basic units of compact bone, consisting of tightly packed concentric rings of tissue with a blood vessel running through the central channel.

parathyroid hormone (PTH): A hormone that regulates calcium levels. It prevents the level of blood calcium from going too low by stimulating the breakdown of bone. In addition to triggering bone loss, it can stimulate bone formation. Given appropriately, it can increase bone mass, and is used as a treatment for osteoporosis.

peak bone mass: The greatest amount of bone tissue that a person has during his or her life; typically reached by age 30.

primary osteoporosis: Bone loss that doesn't result from an identifiable pathological process.

remodeling: The body's mechanism for systematically removing old bone tissue and replacing it with new bone to preserve the strength of the skeleton.

resorption: The removal of bone tissue — both protein and minerals — by osteoclasts.

secondary osteoporosis: Bone loss associated with an identifiable medical condition, treatment with certain drugs, or immobility.

trabecular bone: Bone tissue arranged in a meshwork of thin plates or beams that is commonly found at the center of long bones and that composes a large part of the hip and vertebrae. Also called cancellous bone or spongy bone.

vitamin D: A hormone that plays a key role in ensuring the absorption of calcium from the intestines.

Source: from Harvard Health Publications, Copyright © 2008 Harvard University. All rights reserved. Harvard Medical School does not endorse products.
Used with permission of StayWell.
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