Calcium 1 (revision)

Question 1

Compare and contrast osteoporosis vs osteomalacia.

Answer 1

Osteoporosis - loss of bone mass, whereas osteomalacia is a lack of bone mineral density.

Osteomalacia - low VIT D causes low calcium, which in turn causes high PTH, which causes calcium retention and phosphate loss, hence low phosph, also high ALP because osteoBLASTs are trying to make new strong bone and release ALP.

Osteoporosis - normal everything except bone mass

Question 2

What is rickets vs osteomalacia?

Answer 2

Rickets - childhood disease
Osteomalacia - adulthood disease

Question 3

Is osteomalacia due to low vitamin D or low calcium?

Answer 3

LOW VITAMIN D

this is what causes the low calcium

Question 4

What type of pseudo-fracture do you see in osteomalacia?

Answer 4

Looser’s zones

Question 5

What signs do you see in rickets/osteomalacia?

Answer 5

Bowing of the legs
Muscle pain
Widened epiphyses at the wrist
Costochondral swelling

Question 6

What sign might you see on x-ray with rickets?

Answer 6

Rosary sign due to costochondral swelling

Question 7

What are the causes of osteomalacia besides lack of sunlight?

Answer 7

Drugs - phenytoin
Renal failure - lack of 1 alpha hydroxylase
Pregnancy - baby steals your vit D and calcium
Malabsorption disorders
Phytic acid in chappatis

Question 8

If a child has epilepsy and is prescribed phenytoin, they should be given vit D. Why?

Answer 8

Because phenytoin activates a liver enzyme called 24 hydroxylase, which adds a hydroxyl group to the wrong part of cholecalciferol, so the vit D gets broken down instead of further metabolised.

Question 9

What is the substance in chapathis that causes low vit D?

Answer 9

Phytic acid

Question 10

What scores are used in DEXA scans? What scores indicate what?

Answer 10

T score and Z score

T score - bone mineral density compared with young matched individuals

Z score - bone mineral density compared with age matched individuals to see relative loss

T score BELOW -2.5 = osteoporosis.
T score BETWEEN -1 and -2.5 = osteopenia

Question 11

What lifestyle factors can cause osteoporosis?

Answer 11

Lifestyle - EtOH, smoking, being sedentary

Question 12

What endocrine diseases can cause osteoporosis?

Answer 12

Endocrine - hyperprolactinemia, hyperthyroidism, Cushings

Question 13

What other causes can cause osteoporosis?

Answer 13

Genetics, prolonged illnesses causing immobility

Question 14

What drugs can cause osteoporosis?

Answer 14

Steroids

Question 15

Why does hyperprolactinemia cause osteoporosis?

Answer 15

Shuts down FSH and LH so no oestrogen produced by granulosa cells of ovum.

Question 16

Why does hyperprolactinemia cause osteoporosis?

Answer 16

Shuts down FSH and LH so no oestrogen produced by granulosa cells of ovum.

Question 17

How do you prevent osteporosis?

Answer 17

Weight bearing exercise

Question 18

How can you ‘treat’ or manage osteoporosis?

Answer 18

Vit D
Calcium
Bisphosphonates
PTH
Ca analogues - strontium
HRT
SERMs

Question 19

How should bisphosphonates be taken?

Answer 19

Bisphosphonates should be taken on an empty stomach and definitely not with calcium as it will just bind to calcium otherwise and get pooped out.

Question 20

What is a key side effect of bisphosphonates? How does this change how it’s taken?

Answer 20

Gastric irritation - so you shouldn’t take it and go back to bed, you need to be upright and take lots of water so it’s washed down properly

Question 21

What can be given as an alternative to oral bisphophonates?

Answer 21

IV alendronate once a year

Question 22

How do bisphosphonates work?

Answer 22

Reduce bone resorption as it can’t be broken down once in bone

Question 23

Give an example of a PTH drug

Answer 23

Teriparatide

Question 24

How does teriparatide work for osteoporosis?

Answer 24

It increases bone formation (paradoxical, since PTH normally causes bone resorption, but in this case it causes bone formation because it is given in intermittent daily doses, rather than continually as the body would give it in hyperparathyroidism.

See this paper and this quote:

https://www.ncbi.nlm.nih.gov/books/NBK559248/#:~:text=Mechanism%20of%20Action,-Effects%20on%20Bone&text=To%20exert%20its%20catabolic%20effects,and%20macrophage%20colony%2Dstimulating%20factor.

It turns out that the difference in PTH effects on the bone stem from differences in the dose and pattern of exposure of bone to it. When under continuous exposure to PTH (e.g., hyperparathyroidism), bone undergoes resorption more than formation, while intermittent exposure to low-dose PTH (like daily administration of teriparatide) induces bone formation more than resorption.

Question 25

What is strontium?

Answer 25

Calcium replacement but not very strong

Question 26

What is a SERM example?

Answer 26

Tamoxifen
Raloxifene

Question 27

How does Tamoxifen work?

Answer 27

Tamoxifen is great in reducing breast cancer and increasing bone density - antagonist in breast, agonist in bone