• Bisphosphonates: A class of compounds, including alendronate, etidronate, risedronate and zoledronic acid, that slow bone resorption and are used to treat osteoporosis
• Bone mass: The total amount of bone tissue in the body
• Bone mineral density (BMD): The amount of mineralised bone tissue in a given area, usually calculated as grams per square centimetre
• Calcitonin: A naturally-occurring hormone that helps regulate calcium in the body. Available as an injection or a nasal spray, calcitonin is approved by the FDA for the treatment of osteoporosis
• 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
• Combined hormone replacement therapy (combined HRT): Replacement of a woman’s declining hormones with oestrogen and progestin or progesterone
• 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. It is 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. It can result from compression fractures of vertebrae and is commonly called dowager’s hump
• Dual energy x-ray absorptiometry (DEXA®): A test in which x-rays are used to measure bone density and produce an image of the bone; the preferred means of osteoporosis testing  
• Fluoride: Sodium fluoride is a compound that can increase bone density and is under study for treating osteoporosis
• Glucocorticoid: A class of hormones produced by the adrenal gland and simulated by pharmaceutical preparations such as prednisone
• Growth factors: Substances produced by the body that stimulate tissue growth; some growth factors are under investigation for use in preventing and treating osteoporosis
• 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
• Kyphoplasty: A minimally invasive procedure to alleviate pain from vertebral compression fractures. An orthopaedic balloon is placed in the affect vertebra and inflated; the resulting cavity is filled with bone cement in order to stabilise the vertebral fracture
• Oestrogen-replacement therapy (ERT): Replacement of a woman’s declining hormones with oestrogen alone
• Osteoblast: A bone-forming cell
• Osteoclast: A bone-removing cell
• Osteocyte: An osteoblast that has completed its bone-forming function and has become trapped in new bone tissue
• Osteoprotegerin (OPG): A protein found naturally in the body that reduces the production of osteoclasts. It is under investigation as a potential osteoporosis treatment
• Osteon: The basic unit of compact bone, consisting of tightly packed concentric rings of tissue with a blood vessel running through the central canal
• Parathyroid hormone (PTH): a hormone that prevents the level of blood calcium from going too low and can stimulate the breakdown of bone. When given intermittently, it can increase bone mass. It’s under investigation 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
• Phyto-oestrogens: Plant compounds that have oestrogen-like effects. They are being studied as a treatment for osteoporosis
• Postmenopausal osteoporosis: Bone loss resulting from the deficiency of oestrogen associated with menopause; also known as Type 1 osteoporosis
• Progestin/progestogen: A synthetic progesterone
• Progesterone: A natural hormone. It (or its synthetic cousin, progestin) is often added to oestrogen treatments to reduce the woman’s risk for endometrial cancer
• Primary osteoporosis: Bone loss that doesn’t result from an identifiable pathological process
• Raloxifene: A selective oestrogen receptor modulator (SERM) that slows bone loss. It has been approved for use in the prevention and treatment of osteoporosis
• 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 mineral salts – by osteoclasts
• Selective oestrogen receptor modulators (SERMs): Medications that are designed to deliver the benefits of oestrogen without its negative side effects. SERMs include raloxifene and tamoxifen
• Secondary osteoporosis: Bone loss associated with an identifiable medical condition, treatment with certain drugs, or immobility
• Trabecular bone: Bone tissue arranged in a mesh-work of thin plates or beams that is commonly found at the centre of long bones and that composes a large part of the hip and vertebrae; also called cancellous bone or spongy bone
• Type 1 osteoporosis: Primary osteoporosis in which bone loss is due to the oestrogen decline associated with menopause
• Type 2 osteoporosis: Primary osteoporosis in which bone loss is due to aging
• Ultrasound devices: Diagnostic tools that use high-frequency sound waves to measure internal body structures. The newest type of bone density-measurement equipment; used to measure bone in the heel, shin, or kneecap
• Vertebrae: the cylindrical bones that comprise the spinal column
• Vertebroplasty: A minimally invasive procedure to stabilise compressed vertebrae and alleviate pain. A needle is inserted into the compressed portion of a vertebra and surgical cement is injected in it
• Vitamin D: A hormone that plays a key role in ensuring the absorption of calcium from the intestines

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