Bone Health Glossary:
Bone loss:
A condition in which there is a decrease in the amount and thickness of bone tissue.
Bone gain:
Even though bones stop growing in length in early adulthood, they can continue to increase in thickness or diameter throughout life in response to stress from increased muscle activity or to weight. The increase in diameter is called appositional growth. Osteoblasts in the periosteum form compact bone around the external bone surface. At the same time, osteoclasts in the endosteum break down bone on the internal bone surface, around the medullary cavity. These two processes together increase the diameter of the bone and, at the same time, keep the bone from becoming excessively heavy and bulky.
BMD:
A measure of the amount of minerals (mostly calcium and phosphorous) contained in a certain volume of bone. BMD measurements are used to diagnose osteoporosis (a condition marked by decreased bone mass), to see how well osteoporosis treatments work, and to predict how likely the bones are to break. Low BMD can occur in patients treated for cancer also called bone density, bone mass, and bone mineral density.
DEXA:
A procedure that measures the amount of calcium and other minerals in a bone by passing X-rays with two different energy levels through the bone.
Fracture:
A fracture is a partial or complete break in the bone. There are many different types of fractures.
FRAX:
FRAX is a population-specific algorithm that estimates the absolute risk of fracture to aid in screening and treatment decisions in the general population. Studies suggest that FRAX underestimates fracture risk in HIV-infected men; however, both studies included men under 50 years of age and compared the FRAX score to either BMD outcomes or prevalent fractures instead of incident fractures. Further study is required to evaluate the contribution of chronic HIV infection and ART on fracture risk and to clarify screening algorithms and treatment thresholds in HIV-infected individuals.
Osteopenia:
A condition in which there is a lower-than-normal bone mass or bone mineral density (the amount of bone mineral contained in a certain amount of bone). Osteopenia is a less severe form of bone loss than osteoporosis.
Osteoporosis:
Osteoporosis causes bones to become weak and brittle — so brittle that a fall or mild stresses such as bending over or coughing can cause a break. Osteoporosis-related breaks most commonly occur in the hip, wrist, or spine.