51 Bone diseases + markers Flashcards
What are the four functions of the bone?
Structural support.
Organ protection.
Blood cell production.
Site of mineral storage.
What are the two layers of bone?
Characteristics?
Cortical bone: outer, hard.
Trabecular: inner, spongy.
What does the extracellular matrix of the bone consist of? (4).
Collagen.
Hydroxyapatite.
Calcium.
Phosphate.
What is osteoid?
Non-mineralised organic matrix consisting of mainly Type 1 collagen.
What is hydroxyapetite?
Calcium-phosphate-hydroxide salt.
Differentiate between the function of osteoclasts and osteoblasts:
Osteoblasts: make bone.
Osteoclasts: resorb bone.
What are osteocytes?
Osteoblasts that are trapped in the bone matrix.
What do osteoblasts make? (4).
Osteoid.
Hormones (osteocalcin).
Matrix proteins.
Alkaline phosphatase.
Which enzymes do osteoclasts produce? (2).
TRAP - tartrate resistant acid phosphatase.
Cathepsin K.
Which hormones regulate osteoclast activity? (3).
PTH.
Calcitonin.
IL-6.
Which ligands are involved in osteoclast maturation? (2).
RANK ligand.
Osteoprotegrin.
What are the functions of osteoclasts? (2)
Mechanosensory.
Regulate bone turnover.
How often is the adult skeleton replaced completely?
10 years.
Describe the bone cycle: (4)
Resting.
Osteoclast resorption.
Osteoblasts make osteoid.
Mineralisation.
Describe how bone mass changes with age.
Peaks at 30.
Decreases with age (sudden drop in menopause in women).
Name the products of active osteoblasts that are measured: (3)
Alkaline phosphatase.
Osteocalcin (OC).
Procollagen type 1 propeptides (P1NP).
What is produced during bone resorption? (3).
Hydroxyproline.
Pyridinium.
Cross-linked telopeptides of type 1 collagen (NTX, CTX).
Where is alkaline phosphatase produced?
Bone (50%).
Liver (50%).
What causes an increase in bone alkaline phosphatase? Generally, then (4).
Increase in bone remodelling. Growth. Fractures. Hyperparathyroidism. Paget's.
Why is P1NP a good marker of bone production? (2).
Low diurnal and intraindividual variation.
No affected by food intake.
What are the problems with using cross linked collagen molecules as markers?
Diurnal variation.
Not correlated with bone density.
Which marker is used to measure the success and compliance of anti-resorptive therapy?
Cross linked telopeptides of type 1 collagen (CTX, NTX).
Which bone marker is used to monitor compliance with terparatide?
P1NP.
How is bone mass measured and quantified?
DEXA scanning.
T score. Between -1 and -2.5 is osteopenia.
Below -2.5 is osteoporosis.