Potent bisphosphonate used for the treatment and prevention of osteoporosis (brand name Fosamax).


Class of drugs which attach to bone tissue and inhibits the resorption of bone by the osteoclasts.

Bone Mineral Density (BMD)

Is a measure of the mineralised content of bone tissue. It is the best predictor for risk of future fractures.

Bone formation

The latter phase of bone remodelling where calcium and phosphate are embedded within the newly formed protein matrix to strengthen the bone and improve its rigidity.

Bone matrix

The network of proteins laid down by the osteoblasts ready for mineralisation.

Bone remodelling

The continual process whereby old bone is resorbed and replaced by formation of new bone.

Bone resorption

The initial phase of remodelling whereby osteoclasts absorb and remove old bone tissue.


Hormone naturally secreted by the thyroid gland which inhibits osteoclasts (bone resorptive cells).


Vitamin D metabolite which increases calcium absorption and enhances bone mineralisation (brand name Rocaltrol).


Essential mineral for the development and maintenance of the skeleton.

Cancellous bone (trabecular bone)

Interior part of the bone with a spongy-like or porous structure.

Cortical bone

The compact or dense outer layer of bone.

Dual photon absorptiometry (DPA)

Bone density test using photons from a radionuclide source at 2 different energy levels. Has been replaced by the DEXA test.

Dual energy x-ray absorptiometry (DXA or DXA)

The 'gold standard' in measuring bone density. Uses photons from an x-ray source at 2 different energy levels.


Female steroid hormone that reduces the rate of bone resorption. Also aids in calcium absorption from gut and renal retention of calcium.


Bisphosphonate used in the treatment of osteoporosis (brand name Didrocal).


Osteoporotic breakage of bone caused by low bone mass.

Hormone replacement therapy (HRT)

Generalised term used to describe an estrogen replacement therapy given to female patients after menopause.

Low bone mass (osteopenia)

A measurement of bone density where the T-score is between 1 and 2.5 standard deviations below the young adult mean reference population.


Time in a woman’s life where ovaries cease functioning and estrogen levels fall - time of last menstrual period.


Cells involved in repairing damaged bone, replacing old bone tissue and forming new bone.


Cells involved in removing old bone tissue.


See low bone mass.


Clinical condition whereby there is low bone mass and a change in micro architectural structure leading to bone fragility and increased risk of fractures.

Peak bone mass

The stage of skeletal growth when the bones have reached their maximum bone mass. It occurs at the young adult stage.

Quantitative computed tomography (QCT)

Bone density test that measures the volume of the bone - usually the trabecular bone of the lumbar spine. Other sites cannot be measured.


Selective estrogen receptor modulator (SERM) -specific anti-osteoporotic medication used for the treatment and prevention of osteoporosis. It does not stimulate the breast or endometrium (brand name Evista).


A bisphosphonate with anti-resorptive properties. Used for the treatment and prevention of osteoporosis (brand name Actonel).

Single photon absorptiometry (SPA)

Test using single photon energy to measure bone density at the peripheral sites such as heel and forearm.

Standard deviation

Measurement of variation from a mean or "normal" value.

Single energy x-ray absorptiometry (SXA)

Bone density test used for measurement of peripheral sites only, however it cannot differentiate cortical and trabecular bone It has superseded the SPA test.

Trabecular bone

See cancellous bone.


Measurement used in bone densitometry. It is the number of standard deviations above or below the mean for a young adult reference population.


Test used to assess bone density at the heel. Useful as a pre-screening tool for osteoporosis.

Vitamin D

Nutrient formed in the skin on exposure to sunlight. It is essential to maximise calcium absorption from the diet.


Measurement used in bone densitometry. It is the number of standard deviations above or below the mean for an age matched reference population.