Diseases of Human Systems - connective tissue disease (bone) Flashcards
List the 3 key features of bone.
Load bearing
Self repairing
Dynamic - continuously adapting = can adapt to its environment
What are the functions of calcium?
It maintains nerve and muscle function
What is the role of the parathyroid hormone in relation to calcium? (2)
It regulates calcium
Ensures calcium is transported to the correct location.
Describe hypoparathyroidism
When there is low serum calcium from insufficient amounts of parathyroid hormone
Name the two types of hyperparathyroidism
Primary
Secondary
What causes primary hyperparathyroidism?
Problems with the glands themselves i.e. tumours
What is the outcome of primary hyperparathyroidism?
High serum calcium and inappropriate activation of osteoclasts to resorb bone
What causes secondary hyperparathyroidism?
Kidney failure
Vitamin D deficiency
- low sunlight exposure
- GI disease = poor absorption
- drug interactions
What is the outcome of secondary hyperparathyroidism?
where there is appropriate activation of osteoclasts which causes bone resorption in response to low serum calcium in order to raise it
What are sources of vitamin D?
Sunlight
Food - OJ and fish
Describe how sunlight produces vitamin D.
Cholecalciferol is produced by the skin absorbing sunlight.
Cholecalciferol is transported to the blood and then travels to the liver and kidneys where it is processed.
The processing creates the active form which can be absorbed by the gut; 1, 25 - dihydroxycolecalciferol.
what is the active and absorbable form of vitamin D?
1, 25 - dihydroxycolecalciferol.
What are the barriers to absorbing vitamin D?
Low sunlight exposure - housebound individuals, dark skinned people in northern countries.
Poor GI absorption - those with intestinal diseases such as crohns and UC.
Drug interactions - anti-epileptics such as carbamazepine and phenytoin
What is osteomalacia?
When healthy bone matrix is formed but it is not calcified properly after bone formation
What are the effects of osteomalacia? (3)
Vertebral compression and pain in the lower limbs
Muscle weakness
Nerve effects such as trousseau and Chvostek signs
What is rickets?
When healthy bone matrix is formed but it is not calcified properly DURING bone formation due to a lack of vitamin D or Ca
What causes rickets and osteomalacia?
A calcium deficiecny
What investigations can we do for osteomalacia? (3)
measure;
Serum calcium - decreased
Serum phosphate - will be decreased
Alkaline phosphatase - will be very high
How do we manage osteomalacia? (4)
We must correct the cause of the calcium deficiency;
Malnutrition - increase consumption of Ca
Correct the GI disease
Increase sunlight exposure 30 mins 5x a week
Provide a dietary supplest of vitamin D
What is the relationship between vitamin D and Ca?
The active form of vitamin D allows Ca absorption from the gut.
What is osteoporosis?
Reduced healthy bone mass - inevitable reduction with age
What are the risk factors for osteoporosis?
Age
Sex - female
Deficient in oestrogen and testosterone
Early menopause
Cushing syndrome - high levels of cortisol
Genetic links
Race - caucasian and asian
Patient factors - inactivity, smoking, alcohol, poor dietary ca
Drug use - anti-epileptics and steroids
Why are women at risk of osteoporosis?
Women have a lower peak bone mass than men - easier for them to reach the threshold for osteoporosis quicker.
Woman after menopause have a reduction in oestrogen (oestrogen promotes bone mass)
What are the effects of osteoporosis?
More prone to fracture of long bones and the hip.
Shrinkage in height due to scoliosis (lateral bend of spine) and kyphosis (bending of the spine)
How can we prevent osteoporosis? (3)
Build peak bone mass by exercising and having a high dietary Ca intake
Reduce rate of bone mass loss by (the above) and HRT of oestrogen
Pharmacological methods - Bisphosphonates e.g. alendrotnic acid
What are the risks of oestrogen HRT?
Increased risk of breast cancer
Increased endometrial cancer risk - can be combated by progesterone
