Bisphosphonates: A family of non-hormonal drugs used to treat osteoporosis.

Bone densitometry: A test which detects low bone density. The most common bone density test is called dual energy x-ray absorptiometry (DEXA). The test involves lying on a table for 10 to 20 minutes while a small x-ray detector scans the spine, hips or both.

Bone density: The volume of calcium and minerals within the bone tissue.

Bone mass: The total amount of bone tissue in the skeleton.

Calcitonin: Is a hormone involved in calcium regulation.

Cartilage: The translucent and elastic tissue that composes most of the skeletal system during the early years of growth and development. Cartilage covers the articular surfaces of the bone and helps keep bone flexible.

Collagen: An insoluble protein fiber that is the primary component in connective tissue (skin and tendons) and bone.

Corticosteroids: Any number of hormonal steroid substances secreted from the adrenal glands; corticosteroids permit many biochemical processes to proceed at optimal rates (eg: prednisone).

Estrogen: A hormone usually associated with promoting the development of female secondary sex characteristics. Also a component of hormone replacement therapy.

Hard bone: Also known as compact cortical bone; the dense outer covering of a bone that surrounds trabecular bone; the outside surface of bone.

Hormone: A chemical messenger within the body that is secreted by one type of cell and acts on another type of cell.

Hyperthyroidism: Excessive activity of the thyroid gland, resulting in increased metabolic rate, rapid heart rate, and high blood pressure and may cause enlargement of the thyroid gland.

Malabsorption: The inability to adequately or efficiently absorb nutrients from the intestinal tract.

Ossification: The natural process of bone formation.

Osteoblast: Cells that form bone.

Osteoclast: Cells that break down bone.

Osteocyte: A cell that resides within special regions of adult bone and is involved in the maintenance of that bone.

Osteogenesis: The formation of bone in connective tissue or cartilage.

Osteomalacia:  Also known as "adult rickets." A softening of the bones due to vitamin D deficiency.

Osteopenia: A condition characterized by a decrease in bone density less severe than osteoporosis.

Parathyroid hormone (PTH): A hormone secreted by the parathyroid gland that regulates calcium in the body.

Peak bone mass: The maximum amount of bone one can achieve during skeletal growth.

Primary osteoporosis: The term used to describe the rapid bone loss that can occur after menopause or as we age. Apart from the loss of ovarian function, it is not known what causes primary osteoporosis. It can also affect young (premenopausal) women and young men.

Remodeling: The process of replacing old bone with new bone through the action of osteoclasts and osteoblasts.

Resorption: The breakdown and assimilation of bone through the action of osteoclasts.

Secondary osteoporosis: Bone loss caused by other diseases or drug treatments and can affect a person at any time during his/her life.

SERMs (selective estrogen receptor modulator): A family of drugs for use in preventing osteoporosis in postmenopausal women. SERMs act like estrogen in some tissues, while at other times blocking the effects of estrogen. That is why they are said to be selective.

Skeletal system: The bony framework supporting the soft tissues and protecting the internal organs.

Spongy bone: A lattice-like structure of bony tissue that makes up the inner portion of bone.

Vertebrae: Any one of the thirty-three bony segments of the spinal column.