Calcium And Phosphate Metabolism

Question 1

What is osteoporosis?

Answer 1

Loss of bone mass (matrix and organic material)

Question 2

What are the causes of osteoporosis?

Answer 2

Endocrine
Malignancy
Drug - induced
Renal disease
Nutrion
Age

Question 3

Why does osteoporosis make bones more prone to fracture?

Answer 3

Thinning of corticol and trabecular bone making bones weaker and prone to breakage when normal bone won’t break on same impact

Question 4

How do you diagnose osteoporosis

Answer 4

Measure bone mineral density (BMD) using dual X ray absorptiometry (DEX and DXA scan)
- T score and Z score

Question 5

What are the T score measurements for diagnosing osteoporosis

Answer 5

Normal - between 0 and -1
Osteopenia - less than -1 and more than -2.5
Osteoporosis - -2.5 and lower
Severe osteoporosis - lower than -2.5 and presence of at least one fragility fracture

Question 6

What are the endocrine causes of osteoporosis?

Answer 6

Hypogandism - esp estrogen deficiency (menopause in women and enzyme that converts androgens to estrogen deficiency in men)
Excess glucocorticoids - endogenous (untreated Cushings) and exogenous (medications)
Hyperparathyroidosm - parathroid hormone favours bone resorption
Hyperthyroidism

Question 7

What causes estrogen deficinecy?

Answer 7

menopause in women
Men produce less estrogen but normally produce androgens to estrogens , deficiency in the enzyme that converts from androgens to estrogens causes estrogen deficiency

Question 8

What causes excess glucocorticoids?

Answer 8

Untreated cushings if endogenous

Glucocorticoid treatment if exogenous

Question 9

How does hyperparathyroidism cause osteoporosis??

Answer 9

Parathyroid hormone favours bone resorption

Question 10

How does bone density change in people over time?

Answer 10

Peaks at certain age then decreases with age

Question 11

What reasons might cause osteoporsis to happen early in women…? worded dunno

Answer 11

Not normal if peak is too early or too low after which it decreases normally and reaches critical bone loss sooner

Menopause is too early causing quicker drop in bone mass and estrogen

Question 12

What are the treatments for osteoporosis and the mechanism of action for each?

Answer 12

Adequate calcium and vit D intake to prevent
Bisphosphonates - inhibits function of osteoclasts so less bone turnover
PTH analogues - reduce parathyroid hormone release, doesnt favour bone resorption
Denosumab - monoclonal antibody against RANK ligand (RANK activates osteoclasts)
Romosozumab - monoclonal antibody against sclerostin (sclerostin normally breaks down Wnt signalling so stops osteoblast differentiation and bone formation)

Question 13

What is osteomalacia?

Answer 13

Loss of BONE MINERALISATION

Question 14

What are signs of osteomalacia?

Answer 14

permanent defomalities in bone growth (rickets in children) because it makes bones SOFT
Diffuse aches and pains
Chronic fatigue
Weak bones

Question 15

What are the signs in blood of osteomalacia?

Answer 15

Low Calcium and phosphates
Elevated alkaline phosphatase - indicated bone turnover
elevated PTH

Question 16

What are the causes of osteomalacia?

Answer 16

Vitamin D deficiency
Mutations leading to errors in vitamin D metabolism
Hypophosphatemia
Renal disease

Question 17

What is the treatment for osteomalacia mostly on?

Answer 17

Vitamin D and calcium since those are the most common causes of osteomalacia

Question 18

How does osteomalacia present differently in children compared to adults

Answer 18

Rickets due to soft bones in children

Aches, pains, chronic fatigue and weak bones in adults

Question 19

What 2 mutations lead to osteomalacia?

Answer 19

1a hydroxylase mutation causing vitamin D dependent rickets type 1
Vitamin D receptor mutation 2 causing vitamin D dependent rickets type 2

Question 20

What is calcitriol?

Answer 20

Active form of calcium

Question 21

How is calcium converted to calcitriol?

Answer 21

Converted to active form in kidney by alpha hydroxylase enzymes

Question 22

What factors regulate vitamin D (calcitriol)?

Answer 22

Vitamin D increased by:
- PTH
- Low calcium
- Low Pi
Vitamin D decreased by:
- FGF-23
- High calcium
- High Pi

Question 23

What are the levels of calcium, phosphate, vitamin D, calcitriol, PTH of osteomalacia caused by Vitamin D deficiency?

Answer 23

Low calcium
Low phosphate
Low vitamin D
Normal calcitriol
High PTH

Question 24

What is the hallmark of vitamin D deficiency?

Answer 24

Low calcium (hypocalcemia)