Bone Disorders

Question 1

Discuss the calcium storage in bones and bone cells

Answer 1

Bones have the majority storage of calcium in the body, though organic osteoids (un myelinated bone) and inorganic mineral component.

Bone cells:

1. Osteoclasts - release lysosomal enzymes which break down bone (bone resorption)
2. Osteoblasts - synthesis osteoid and participate in mineralisation/ calcification of osteoid (bone formation).

Osteoclast differentiation: RANK ligand expressed on osteoblast surface, RANKL - receptor to stimulate osteoclast formation and activity. So osteoblast express receptors for PTH and calcitrol. This regulates balance between bone formation and resorption = osteoclast binds to osteoblast to be activated and differentiate.

Question 2

Describe the effects of vitamin D deficiency effects on bone

Answer 2

1. In children, rickets. Causes soft bendy soft bone : affects cartilage of epiphysis love growth plates and bone and skeletal abnormalities and pain, growth retardation and increased fracture risk.
2. Adults: osteomalacia. After the epiphysial closure, causes skeletal pain, increased fracture risk and proximal myopathy.

Question 3

Describe the effects of hyperparathyroidism

Answer 3

1. Adenoma - high PTH and high Ca
2. Low plasma Ca eg renal failure, vit D deficiency - High PTH and low or normal Ca
3. Chronic low Ca - high PTH and high Ca

Question 4

Describe the effects of renal failure and bone disease.

Answer 4

Renal function decreases, causes low calcitrol and low calcium absorption, low phosphate excretion so high plasma phosphate. Hypocalcaemia - low bone mineralisation, High PTH, high bone resorption, osteotitis fibrosa cystica.

Question 5

Describe the treatment methods of osteitis (hyperparathyroid bone disease)

Answer 5

1. Hyperphosphataemia: low phosphate diet, phosphate bindus, reduces phosphate absorption
2. Alphacalcitrol - calcitrol analogue
3. Parathyroidectomy - in tertiary hyper parathyroid indicated for hypercalcaemia and hyperparathyroid bone disease

Question 6

Describe osteoporosis and compare it to osteomalacia

Answer 6

Osteoporosis: condition of reduced bone mass and distortion of bone microarchitecture, having bone mineral density (<2.5)

Compare: both pre-dispose to fracture, but osteomalacia (Vit D deficiency) is causing the inadequacy mineralised bone. Different serum biochemistry …..

Question 7

Describe the treatment options for osteoporosis

Answer 7

1. Oestrogen HRT - anti resorptive effects on skeleton, prevents bone loss, woven intact uterus at risk of endometrial so given progesterone but risk of cancer and DVT
2. Bisphosphonates - bind avidly to hydroxyapatite and ingested by osteoclasts, ingested by osteoclasts to reabsorb bone, promote osteoclast apoptosis reduces bone turnover
3. Denosumab: prevents osteoclast being switched on
4. Teriparatide.

LOOK AT NOTES FOR ALL 4

Question 8

Describe the pages disease of the bone

Answer 8

Accelerated, loacalised but disorganise bone remodelling, excessive bone resorption followed by a compensatory increase in bone formation

LOOK AT NOTES
A