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Glossary
Quick reference for medical terms used in this guide.
A
Alendronate (Fosamax) A bisphosphonate medication that slows bone breakdown. Taken as a weekly pill.
Anabolic (bone drug) A medication that stimulates new bone formation, rather than just slowing breakdown. Examples: teriparatide, romosozumab.
Antiresorptive A medication that slows bone breakdown (resorption). Examples: bisphosphonates, denosumab.
Aromatase An enzyme that converts testosterone to estrogen. Important for bone health in men.
B
Bisphosphonate A class of medications that bind to bone and slow osteoclast activity. Examples: alendronate, risedronate, zoledronic acid.
BMD (Bone Mineral Density) A measurement of how much mineral (primarily calcium) is in a given area of bone. Measured by DXA scan.
Bone marker A blood or urine test that measures the rate of bone formation or breakdown. Examples: CTX, P1NP.
Bone remodeling The continuous process of breaking down old bone and building new bone.
C
Calcium carbonate A form of calcium supplement that requires stomach acid for absorption. Should be taken with food.
Calcium citrate A form of calcium supplement that doesn't require stomach acid. Can be taken with or without food.
Cortical bone The dense, hard outer shell of bone. Makes up about 80% of the skeleton by weight.
CTX (C-terminal telopeptide) A bone turnover marker that measures bone breakdown (resorption). Must be drawn fasting.
D
Denosumab (Prolia) An injectable medication that blocks RANKL, dramatically reducing bone breakdown. Given every 6 months.
DXA (DEXA) scan Dual-energy X-ray absorptiometry. The standard test for measuring bone mineral density.
E
Estradiol The primary form of estrogen. Critical for bone health in both women and men.
Estrogen A hormone essential for bone health. Protects bones by reducing osteoclast activity.
F
FRAX A tool that calculates 10-year fracture risk based on bone density and clinical risk factors.
Fragility fracture A fracture that occurs from minor trauma (like falling from standing height) that wouldn't normally break healthy bone.
H
HRT (Hormone Replacement Therapy) Estrogen (with or without progesterone) given to women to replace hormones lost at menopause.
Hyperparathyroidism A condition where the parathyroid glands produce too much PTH, leading to bone loss.
O
OPG (Osteoprotegerin) A protein that blocks RANKL, reducing bone breakdown. Acts as a natural brake on osteoclasts.
Osteoblast A cell that builds new bone.
Osteoclast A cell that breaks down (resorbs) bone.
Osteocyte A mature bone cell embedded within bone. Senses mechanical stress and coordinates remodeling. Makes up 90-95% of bone cells.
Osteopenia Bone density lower than normal but not low enough to be classified as osteoporosis. T-score between -1 and -2.5.
Osteoporosis A condition of low bone density and deteriorated bone structure, leading to increased fracture risk. T-score of -2.5 or lower.
P
P1NP (Procollagen type 1 N-terminal propeptide) A bone turnover marker that measures bone formation.
Peak bone mass The maximum bone density achieved, typically by age 25-30.
Periosteum The membrane covering the outer surface of bones. Contains cells that can form new bone.
PPI (Proton Pump Inhibitor) A class of acid-reducing medications (omeprazole, etc.) that can affect calcium absorption with long-term use.
PTH (Parathyroid Hormone) A hormone that regulates calcium levels. Can break down or build bone depending on how it's delivered.
R
RANKL A signaling molecule that activates osteoclasts to break down bone.
Resorption The process of bone breakdown by osteoclasts.
Romosozumab (Evenity) A medication that blocks sclerostin, increasing bone formation while reducing breakdown.
S
Sclerostin A protein that inhibits bone formation. Blocking it with medication increases bone building.
SHBG (Sex Hormone Binding Globulin) A protein that binds to sex hormones. High levels mean less "free" hormone available.
T
T-score A comparison of your bone density to that of a healthy young adult. Used to diagnose osteoporosis.
TBS (Trabecular Bone Score) An analysis of DXA images that provides information about bone microarchitecture.
Teriparatide (Forteo) A daily injectable medication containing a portion of PTH. Stimulates new bone formation.
Testosterone The primary male sex hormone. Important for bone health in both sexes.
Trabecular bone The spongy, honeycomb-like bone found inside bones, especially at the spine and ends of long bones.
TRT (Testosterone Replacement Therapy) Testosterone given to men with confirmed low levels.
V
Vitamin D (25-OH vitamin D) A vitamin essential for calcium absorption. Most people need supplementation.
Volumetric BMD True bone density measured as grams per cubic centimeter. Measured by QCT, not standard DXA.
Z
Z-score A comparison of your bone density to others of your same age and sex.
Zoledronic acid (Reclast) A bisphosphonate given as a yearly IV infusion.