Bone endocrinology

Question 1

What is the composition of human bone?

Answer 1

20% trabecular bone (porous, sponge-like)

80% cortical bone (dense material that provides stiffness and strength)

Question 2

Approximately how much of the adult skeleton is remodelled each year?

Answer 2

10%

Question 3

How is bone remodelled?

Answer 3

Osteoclasts resorb bone at a previously inactive site

These are replaced by osteoblasts which lay down osteoid that is mineralised to form new bone

Question 4

What is the dysfunction of the bone remodelling cycle that causes osteoporosis?

Answer 4

There is an absolute or relative increase in resorption over formation

Question 5

What is the major determinant of bone loss in women following the menopause?

Answer 5

Oestrogen deficiency

Question 6

Which part of the 3D matrix structure of trabecular bone succumbs to bone loss fastest?

Answer 6

Horizontal trabeculae (non-load bearing)

This causes a loss in trabecular thickness

Question 7

What are the risk factors for fracture?

Answer 7

Previous fragility fractures
Current use or frequent past use of oral glucocorticoids
History of falls
Family history of hip fracture
Other secondary causes of osteoporosis
Low BM (<18.5)
Smoker (>10 cigarettes per day)
Alcohol intake >4 units per day

Question 8

What is the risk of having a hip fracture with a past history of a Colle’s fracture?

Answer 8

Double fracture risk

Question 9

What are the direct effects of steroid use on bone health?

Answer 9

Reduction of osteoblast activity and lifespan

Suppression of replication of osteoblast precursors

Reduction in calcium absorption

Question 10

What lifestyle advice is there for management of osteoporosis?

Answer 10

High intensity strength training
Low impact weight bearing exercise (standing, one foot always on the floor)
Avoidance of excess alcohol
Avoidance of smoking
Fall prevention

Question 11

What is the recommended dietary intake of calcium for a post-menopausal woman?

Answer 11

1000mg calcium per day