Bone Metabolism Flashcards
What type of bone is most susceptible to Osteoporosis? Why?
Trabecular; turn over quicker (break down/rebuild cycle); With age, build up cannot keep up with break down
Which bones are Trabecular bones
Hips, feet, hands, elbows, vertebrae, wrists
What is the function of Osteoblasts
Bone formation
What is the function of Osteoclasts
Break down bones
What is the function of Calcitonin
Lowers blood Calcium by opposing PTH, inhibiting Osteoclast activity and increasing Calcium secretion in urine
What is the function of Osteocalcin
Attracts Calcium to be deposited into bones; secreted by Osteoblasts
What is the function of Glucocortids in Bone Metabolism
Reduce Calcium absorption & Osteoblast activity; anti-inflammatory steroids
What secretes Osteocalcin
Osteoblasts
What are Glucocortids
Anti-inflammatory steroids; long-term exposure can lead to Osteomalacia or growth failure in children
What is the function of Thyroid Hormone in Bone Metabolism
Increase bone resorption
What is the function of Growth Hormone in Bone Metabolism
Stimulate Calcium deposition into bones
What is the function of Estrogen in Bone Metabolism
Inhibits Osteoclast activity when bound to bones
What secretes Calcitonin
Thyroid
What activates Bone Turnover Cycle
Osteoclasts secrete lysosymes to breakdown (dissolve) calcium phosphate (hydroxyapatite) in bones; also secrete collagenase to dissolve protein backbone; “Cement of bones”; bone resorption
How long does osteoclast activity last in Bone Turnover Cycle
10-20 days
What is the next step in the Bone Turnover Cycle after Osteoclast activity (Step 2)
Osteoblasts deposit minerals; bone formation
How long does osteoblast activity last in the Bone Turnover Cycle
3-6 months
What is the next step in the Bone Turnover Cycle after Osteoblast activity (Step 3)
Resting phase
How long does the resting phase last in the Bone Turnover Cycle
months-years before resorption begins again
What are markers of bone formation (in the blood)
Osteocalcin, Bone-specific alkaline phosphatase, Procollagen peptides
What are markers of bone resorption (in the urine)
Hydroxyproline, Hydroxylsine glycosides, Pyridinium crosslinks
What does high Osteocalcin in the blood indicate
Bone formation
What does Hydroxyproline in the urine indicate
Bone resorption (collagen breakdown)
When does Osteoporosis occur
When there is more bone break down than build up
What are the health concerns with Osteoporosis
Increased risk of breaking bones; potentially effect blood Calcium and other Calcium functions; hunching could effect lung capacity, increasing pneumonia risk
What is the concern with bone breaking in Osteoporosis patients
Bone healing takes a long time, decreases quality of life, muscle atrophy, decreases mortality
At what stage do the size of bones stop growing
Puberty
At what stage does the density of bones stop building (peak bone mass)
Age 30
Why is fracture threshold higher in women
Bone mass lower to begin with, experience steeper decline rate
How does smoking effect bones
Encourages osteoclasts
How can osteoblasts be stimulated
Pressure - weight training/exercise
What is BMD compared with for measuring Osteoporosis during DXA testing
Compare current measurement with someone younger, same gender for osteoporosis diagnosis; Within age, gender and ethnicity group also measured
Osteoporosis vs Osteomalacia
Remodeling imbalance;more breakdown than buildup vs Remineralization low;supply problem (VitD or Calcium;intake or kidney/liver function impaired)
What is similar between Osteoporosis and Osteomalacia
Low bone mineral density (BMD)
What can be tested to differentiate between Osteoporosis and Osteomalacia
Dietary intake, serum Hydroxyprolene, serum VitD, PTH levels
