B / 20 : Agents affecting bone mineral homeostasis (calcium, vitamin D...) Flashcards
1
Q
What is osteoporosis.
A
Low bone mass and deterioration of the microarchitecture of the bone leading to increase in bone fragility and fractures
2
Q
How is bone homeostasis maintained?
A
- Through controlled absorption of Ca and PO in the gut by vitamin D, fibroblast growth factor 23 and PTH (not enough Ça)
- Through Calcitonin which inhibits bone resorption and stimulates renal excretion of serum Ca and PO (too much Ça)
3
Q
Roles of PTH (2)
A
- Reduces Ca excretion and increases PO excretion
- Promotes bone resorption
4
Q
How is PTH controlled? (2)
A
- Regulated via increased Ca : reduces PTH secretion
- Regulated via negative feedback by high calcitriol (vitamin D)
5
Q
How is calcitriol controlled?
A
- PTH stimulates formation in the kidney
- FGF23 inhibits formation in the kidney
6
Q
Roles of calcitriol (vitamin D)
A
- Increases Ca and PO absorption from the gut and kidney
- Induces RANKL in osteoblasts ( + bone resorption if low Ca, - if high)
7
Q
Roles of FGF23 (2)
A
- Inhibits production of calcitriol
- Stimulates renal excretion of PO
8
Q
Roles of calcitonin (3)
A
- Reduces serum Ca and PO
- Inhibits osteoclastic bone resorption
- Inhibits bone formation long term
9
Q
Primary hormonal modulators of bone-mineral homeostasis
A
- Cholecalciferol (vitamin D3)
- Teriparatide
10
Q
Secondary hormonal modulators of bone-mineral homeostasis
A
Raloxifene
11
Q
Non-hormonal modulators of bone-mineral homeostasis
A
- Zoledronate
- Alendronate
- Denosumab
(Denosumab - des nos)
12
Q
Cholecalciferol
- MOA
- Effect
- Indication
- SE
- ROA
A
- Modulates gene expression : vitamin D3
- Increased Ca and PO absorption from GI, decreased Ca and PO excretion in kidney, induces RANKL on osteoblasts
- For vitamin D deficiency, hypothyroidism
- Hypercalcemia, hyperphosphatemia
- Oral
13
Q
Teriparatide
- MOA
- Effect
- Indication
- SE
- ROA
A
- PTH analog
- Net bone formation, increased Ca reabsorption in kidney
- For osteoporosis
- Hypercalcemia, osteosarcoma
- Subcutaneous injection
(Paratide sounds like parathyroid)
14
Q
Raloxifene
- MOA
- Effect
- Indication
- SE
- ROA
A
- Estrogen receptor ANTagonist in breast tissue, partial estrogen agonist in bones
- Inhibits osteoclast differenciation
- 1st line drug in prevention of postmenopausal osteoporosis
- Hot flashes, risk of thromboembolic events
- Oral
15
Q
Zoledronate, Alendronate
- MOA
- Effect
- Indication
- SE
- ROA
A
- Apoptosis of osteoclasts
- Inhibits bone resorption
- For treatment of osteoporosis + paget’s disease + hypercalcemia
- Hypocalcemia, osteonecrosis of jaw, esophagitis
- Oral or parenteral
