Metabolic bone disease

Question 1

What is osteopenia

Answer 1

When bone mass is 1-2.5 standard deviations below peak bone mass

Question 2

What is osteoporosis

Answer 2

When bone mass is >2.5 SD below peak bone mass

Osteopenia that significantly increases risk of bone fracture

Question 3

Name the two most common forms of primary osteoporosis

Answer 3

Senile osteoporosis and post-menopausal osteoporosis

Question 4

What can cause secondary osteoporosis

Answer 4

Endocrine disorders, GI disorders, or drugs

Question 5

Why is osteoporosis common in elderly

Answer 5

As osteoblasts age, they become less responsive to growth factors

Question 6

WHy does inactivity (common in elderly) lead to osteoporosis

Answer 6

Mechanical factors stimulate bone remodelling

Load magnitude influences bone density. Resistance exercise better than repetitive endurance

Question 7

How can dietary imput contribute to osteoporosis

Answer 7

Low calcium intake (common in adolescent girls) restricts peak bone mass

Question 8

How does the menopause influence bone mass

Answer 8

Oestrogen deficiency contributes to osteoporosis due to high turnover

Question 9

Is DVT more likely in patients with osteoporosis who suffer a fracture

Answer 9

yes, specifically dvt from legs

Question 10

What is rickets

Answer 10

Osteomalacia in children as deposition of bone in growth plates is interfered with

Question 11

What is osteomalacia

Answer 11

Bone formed during remodelling is undermineralised, predisposition to fractures. Unmineralised matrix accumulates

Question 12

Which foods are vitamin D found in

Answer 12

Oily fish, beef liver, cheese, egg yolk

Question 13

Why is vitamin D needed

Answer 13

To maintain Plasma calcium and phosphorous for metabolic functions, bone mineralisation, neruomusular function

Question 14

What role does light play in vitamin D synthesis

Answer 14

Converts 7-Dehydro-cholesterol into cholecalciferol vit D3

Question 15

What happens to Vit D3 once synthesised.

Answer 15

Binds to D-binding protein (DBP) and transported to the liver, converted by 25-hydroxylase to 25 hydroxy-vitamin D

Question 16

What happens to 25-hydroxy-vitamin D when it circulates to the kidneys

Answer 16

Converted by alpha-1 hydroxylase to form 1-25 dihydroxy vitamin D (most active form)

Question 17

What regulates 1-25 dihydroxy vitamin D production

Answer 17

Hypocalcemia stimulates parathyroid hormone secretion, augmenting conversion by activating alpha 1 hydroxylase

Hypophospataemia directly activates alpha 1 hydroxylase

Increased levels of 1-25 dihydroxy vitamin D downregulates its synthesis inhibiting alpha 1 hydroxylase

Question 18

WHat does active vitamin D do in hypocalcaemic states

Answer 18

it, with PTH, increases resorption of calcium and phosphorous from bone supporting blood levels

Question 19

What does active vitamin D do in normal calcaemic states

Answer 19

Required for calcium deposition in epiphyseal cartilage and osteoid matrix

Question 20

How does vitamin D affect osteoblasts

Answer 20

Upregulates RANKL , activating RANK receptors on osteoclast precursors, developing. Also bone resorption

Question 21

How does Vitamin D affect mineralisation

Answer 21

Stimulates osteoclasts to form osteocalcin (calcium binding protein) promoting calcium deposition

Question 22

What causes vitamin D deficiency

Answer 22

Limited sunligt exposure or poor diet

Less commonly due to renal disorders or malabsorption

Question 23

What happens to calcium levels in Vit D deficiency

Answer 23

Hypocalcaemia, stimulating parathyroid to form PTH, activating renal alpha 1 hydroxylase, increasing active Vit D and calcium adsorption

Restored calcium levels, but phosphate excretion increases. mineralisation of bone impaired

Question 24

What two diseases does Vit D deficiency lead to

Answer 24

Rickets and osteomalacia

Bone loss and fractures in elderly

Question 25

What causes skeletal deformity in rickets

Answer 25

Excess umnineralised bone matric causing skeletal deformity. This is due to inadequate calcification of epiphyseal cartilage, which overgrows into irregular masses. Osteoid matric deposits on catrilainous remnant, enlargement and lateral expansion of osteochondral junction

Question 26

Why is there abnormal overgrowth of capillaries and fibroblasts in rickets

Answer 26

Microfractures and stresses on poorly mineralised and formed, weak bone

Question 27

What is osteomalacia

Answer 27

Inadequate mineralisation of osteoid bone matrix, laid down by osteoblasts. Weak and vulnerable bone to fractures. Vertebral bodies and neck of femur especially

Question 28

Name some of the non-skeletal effects of vitamin D

Answer 28

Enhances immune cell differentiation and inflammation, inhibits tumour cell proliferations, and inhibits angiogenesis

Question 29

What is the main action of PTH

Answer 29

To increase serum calcium: Activates osteoclasts from increased RANKL expression on osteoblasts Increased resorption of calcium from renal tubules, Increases syhtesis of active VIT D

Question 30

What causes primary hyperparathyroidism

Answer 30

benign (usually) tumour of parathyroid

Question 31

What causes secondary hyperparathyroidism

Answer 31

Underlying renal disease causing parathyroid glands to become hyperplastic

Question 32

What happens to cause tertiary hyperparathyroidism

Answer 32

Underlying renal disease causes hyperplasia of parathyroids, develops parathyoid adenoma with autonomous PTH secretion

Question 33

How can secondary hyperparathyroidism bone changes

Answer 33

Restoration of parathyroid hormone levels

Question 34

What does bones stones moans and groans mean in relation to parathyoid adenoma

Answer 34

Bones: Osteoporosis (PTH++), brown tumour of hyperparathyoidism, osteitis fibrosa cystica (cystic spaces) Stones: Nephrolithiasis -Calcium oxalate stones, Nephrocalcinosis is the metastatic calcification of renal tubules Moans - GIT disturbances include constipation, peptic ulcers, acute pancreatitis CNS disturbances - Depression and seizures

Question 35

What is pagets disease characterised by

Answer 35

Increased but disordered and structurally unound bone

Question 36

Name some clinical features of pagets disease of bone

Answer 36

Lion face/skull leading to heavy head Compression of the posterior fossa Anterior bowinf of femurs and tibiae Chalk stick fractures of legs

Question 37

What are the three phases of pagets disease

Answer 37

Osteolytic, mixed, and osteoslcerotic

Question 38

What is renal osteodystrophy

Answer 38

A spectrum of renal disease seen in patient with chronic renal disease, showing bone mineral deficiency