Chapter 9

T-score

A comparison of an individual's bone density to the average peak bone density of a 30-year-old healthy adult.

hypocalcemia

A condition characterized by an abnormally low concentration of calcium in the blood.

hypomagnesemia

A condition characterized by an abnormally low concentration of magnesium in the blood.

calcium tetany

A condition in which muscles experience twitching and spasms as a result of inadequate blood calcium levels.

hypercalcemia

A condition marked by an abnormally high concentration of calcium in the blood.

hypermagnesemia

A condition marked by an abnormally high concentration of magnesium in the blood.

fluorosis

A condition marked by staining and pitting of the teeth; caused by an abnormally high intake of fluoride.

cortical bone (compact bone)

A dense bone tissue that makes up the outer surface of all bones as well as the entirety of most small bones of the body.

osteoporosis

A disease characterized by low bone mass and deterioration of bone tissue, leading to increased bone fragility and fracture risk.

calcium rigor

A failure of muscles to relax, which leads to a hardening or stiffening of the muscles; caused by high levels of blood calcium.

parathyroid hormone (PTH)

A hormone secreted by the parathyroid gland when blood calcium levels fall. It increases blood calcium levels by stimulating the activation of vitamin D, increasing reabsorption of calcium from the kidneys, and stimulating osteoclasts to break down bone, which releases more calcium into the bloodstream.

calcitronin

A hormone secreted by the thyroid gland when blood calcium levels are too high. Inhibits the actions of vitamin D, preventing reabsorption of calcium in the kidneys, limiting calcium absorption in the small intestine, and inhibiting the osteoclasts from breaking down bone.

trabecular bone (spongy bone)

A porous bone tissue that makes up only 20% or our skeleton and is found within the ends of the long bones, inside the spinal vertebrae, inside the flat bones (sternum, ribs, and most bones of the skull), and inside the bones of the pelvis.

collagen

A protein that forms strong fibers in bone and connective tissue.

osteomalacia

A vitamin D-deficiency disease in adults, in which bones become weak and prone to fractures.

rickets

A vitamin D-deficiency disease in children. Signs include deformities of the skeleton, such as bowed legs and knocked knees. Can be fatal.

osteoclasts

Cells that erode the surface of bones by secreting enzymes and acids that dig grooves into the bone matrix.

osteoblasts

Cells that prompt the formation of new bone matrix by laying down the collagen-containing component of bone, which is then mineralized.

dual energy x-ray absorptiometry (DXA or DEXA)

Currently, the most accurate tool for measuring bone density.

bone density

The degree of compactness of bone tissue, reflecting the strength of the bones. Peak is when it's at it's strongest.

bioavailability

The degree to which our body can absorb and utilize any given nutrient.

calcitriol

The primary active form of vitamin D in the body.

resorption

The process by which the surface of bone is broken down by cells called osteoclasts.

remodeling

The two-step process by which bone tissue is recycled; includes the breakdown of existing bone and the formation of new bone.