Bone disease

Question 1

What does Arthritis mean?

Answer 1

• Inflammation of joints

Question 2

What does Arthrosis mean?

Answer 2

• Non inflammatory joint disease

Question 3

What does Arthralgia mean?

Answer 3

• Joint pain

Question 4

What is bone?

Answer 4

• Mineralised connective tissue
• It is load bearing
• It is dynamic (continuously changing)
• It is self repairing

Question 5

What is the bone turnover cycle?

Answer 5

• Bone removed by osteoclasts
• Bone Deposited by osteoblasts
• Osteoclasts eat away at bone matrix
• Replaced by osteoblasts that deposit osteoid matrix
• Matrix undergoes collagen formation/mineralisation
• Bone formation takes 3-6months

Question 6

What is required in bone turnover cycle?

Answer 6

• Correct amounts of
• Calcium
• Phosphate
• Vitamin D

Question 7

Why is bone turnover necessary?

Answer 7

• In order to maintain calcium homeostasis to replace hypermineralised foci with younger tougher tissue
• Restore bone that has become defective through development and propagation of microfractures

Question 8

How are Bone and Calcium linked?

Answer 8

• Bone forms a store for calcium
• Some is exchangeable and some isn’t
• Exchangeable calcium moves from bone to extracellular fluid and calcium absorbed from gut through ECF
• Calcium lost through gut and urine
• Bone and ECF work together and parathyroid hormone used to ensure correct level of calcium maintained

Question 9

Why is it important calcium is maintained at precise level in blood?

Answer 9

• Normal body function
• Involved in nerve and muscle function

Question 10

How does low dietary calcium affect the body?

Answer 10

• Reduction in plasma calcium
• Increased Parathyroid hormone secretion
  1. Increases active vitamin D which increases intestinal calcium absorption
  2. Decreases urinary calcium which increases conservation of dietary calcium
  3. Increases bone loss which increase bone calcium release
• All lead to restoration of normal plasma calcium levels

Question 11

What does the parathyroid hormone do?

Answer 11

• Found in parathyroid glands
• Maintains serum calcium level
• Raises if calcium levels fall
• Increases calcium release from bone
• Decreases renal calcium excretion

Question 12

What is hypoparathyroidism?

Answer 12

• Low conc of parathyroid hormone
• Results in low serum calcium

Question 13

What is hyperparathyroidism?

Answer 13

Primary
- Due to gland dysfunction like a tumour
- Results in high serum calcium
- Inappropriate activation of osteoclasts

Secondary
- Occur when low serum calcium
- Increase activation of osteoclasts to maintain appropriate calcium level

• Both result in increased bone reabsorption (resorption)
• See radiolucency in radiographs on bone where reabsorption occurs

Question 14

How is Vitamin D absorbed by body?

Answer 14

• Can be absorbed from UV ray from sun or from 7-dehydrocholestrol in diet
• Get absorbed as Cholecalciferol in skin
• Becomes bound Cholecalciferol in blood
• Becomes 25-hydroxycholecalciferol in liver
• Becomes 1,25-dihydroxyxolecalciferol in kidneys which is the active component necessary for calcium absorption in the GIT
• Calcium needed for muscle and bone health

Question 15

What foods can you get Vitamin D from?

Answer 15

• Orange juice
• Fish
• Milk
• Supplements

Question 16

What are some vitamin D problems?

Answer 16

Low sunlight exposure can be problem
- Housebound
- Dark skinned in Northern country as they absorb sunlight less efficiently
- Diet is more relied upon

Poor GI absorption
- Due to poor nutrition
- Small intestinal disease can lead to malabsorption

Drug interactions
- Some antiepileptic drugs like carbamazepine, Phenytoin can interfere with vit D synthesis

Vit D deficiency is usually a combo of factors

Question 17

What is Osteomalacia?

Answer 17

• Softening of bones typically through vit D or calcium deficiency
• Normal bone matrix formed but not calcified properly
• Poorly mineralised osteoid matrix
• Poorly mineralised cartilage growth plate
• Normal amount of osteoid but not enough mineralisation so softening occurs

Question 18

What is Osteoporosis?

Answer 18

• Reduced quantity of normally mineralised bone
• Age related change and is inevitable
• Weakens bones so very easily breakable

Question 19

What disease occurs when Osteomalacia occurs during bone formation?

Answer 19

• Rickets develops then turns into osteomalacia when bone formation completed
• Calcium deficiency
• Serum calcium is preserved in expense of bone mineralisation
• When calcium in short supply during bone formation can lead to soft bone developing that can bend under pressure

Question 20

What are the effects on bone of Osteomalacia?

Answer 20

• Bones bend under pressure and can be seen as ‘bow legs’ in children
• Vertebral compression is seen in adults and cause bone aching to touch

Question 21

What are the Hypocalcaemia effects of Osteomalacia?

Answer 21

• Muscle weakness
• Show signs of Trousseau and Chvostek leading to carpal muscle spasm and facial twitching from CN VII tapping

Question 22

What is Alkaline Phosphatase a measure of?

Answer 22

• Measure of bone turnover
• Very high when issues with calcium levels

Question 23

What levels in blood are we expecting with Osteomalacia investigations?

Answer 23

• Serum Calcium decreased
• Serum Phosphate Decreased
• Alkaline Phosphatase Very high
• Plasma creatine increased due to renal cause
• Plasma Parathyroid hormone increased due to secondary hyperparathyroidism

Question 24

How is Osteomalacia managed?

Answer 24

Firstly correct the cause

If malnutrition - Control GI disease and get more vit D in diet via supplement
If sunlight exposure - 30mins X 5weekly

Question 25

What are the risk factors for Osteoporosis?

Answer 25

- Age - Female higher risk Endocrine - Oestrogen and testosterone deficiency increase risk - Cushings syndrome (increase corticosteroid levels in blood- higher risk) Genetic - Family history - Race (caucasian and asian women) - Early menopause Patient factors - Inactivity - Smoking - Excess alcohol use - Poor dietary calcium Medical Drug use - Steroids - Antiepileptics

Question 26

Why do women have higher risk of developing Osteoporosis?

Answer 26

- Males have higher Peak bone mass - Oestrogen withdrawal (during menopause) increases bone mass loss rate in women - Takes longer for men to loss enough bone mass to get to osteoporosis - Expected peak bone mass of men and women a lot closer than 100years ago due to exercise and women being a lot more active

Question 27

What are the effects of Osteoporosis?

Answer 27

Increased bone fracture risk - Applies to long bones - Usually first clinical sign is when a patient falls and breaks their wrist easily Vertebrae can also be affected - Height loss - Kyphosis (curvature of spine causing top of back to appear more rounded) - Scoliosis (Curvature of spine laterally) - Nerve root can be compressed leading to back pain

Question 28

How can Osteoporosis be prevented?

Answer 28

1. Build maximal Peak bone mass - Through exercise and high dietary calcium intake - For young adults - Gain as much bone mass as poss so effects of osteoporosis take longer to occur 2. Reduce rate of Bone mass loss - Continue exercise and calcium intake - Reduce hormone related effects - Not clear if Oestrogen hormone replacement therapy is continually beneficial but most effective if early menopause 3. Reduce drug related effects - Useful when patients have family history - Consider Osteoporosis prevention drugs (bisphosphonates)

Question 29

What is Hormone Replacement Therapy?

Answer 29

Oestrogen only HRT - Reduces osteoporosis risk - Increases breast cancer risk - Increase endometrial cancer risk (patients who haven't had hysterectomy combine with progestogen to reduce risk) - May reduce ovarian cancer risk - Increase DVT risk (Deep vein thrombosis) - Benefit is lost after HRT stops - Bone marrow density returns to normal 5years after HRT stops

Question 30

What are the two types of Bisphonates?

Answer 30

Non-nitrogenous e.g. Etidronate Nitrogenous e.g. Ibandronate, Zoledronate (extremely potent) *dronate*

Question 31

How do Bisphononates work?

Answer 31

- Act by preventing osteoclast working by poisoning osteoclast and reduces number - Reduces osteoclasts then less bone mass removed and preserving bone mass present

Question 32

How effective are Bisphosphonates?

Answer 32

- Extremely effective - Reduce vertebral fracture risk by 50% - Reduce other fractures by 30-50% - Benefit is lost if drug discontinued - Can be combined with HRT