Osteoporosis Flashcards
Outline Ca2+ balance 2 step reaction (1) 3 main hormones (3) main reaction breakdown in liver?(1) PTH actions (3) Calcitriol (3)
1- Liver : VitD3—>calciTRIOL
3 impact hormones :
1-VIT D (as above) increases Ca2+
2-Parathyroid Hormone (PTH) increases ca2+
3-Calcitonin (released from the thyroid gland, decreases blood calcium levels when they become too high )
PTH:when low Ca2+
1-stimulates break down of minerals in bone–>plasma
2-DCT in kidney = reabsorption of Ca2+
3-stimulates the break down on VIT D = calcitriol
What does the Calcitriol do? Calcitriol 1)GUT -increases ca2+ absorption 2)Bone -increases calcification 3)Kidney -retains Ca2+, acts on PCT ( causes reabsorption of Ca2+ )
Action of PTH (3)
PTH:when low Ca2+
1-stimulates break down of minerals in bone–>plasma
2-DCT in kidney = reabsorption of Ca2+
3-stimulates the break down on VIT D = calcitriol
Action of Calcitriol (3)
what is the difference between calcitonin and calcitriol
(1)
Calcitriol = active VITAMIN D 1)GUT -increases ca2+ absorption 2)Bone -increases calcification 3)Kidney- Retains Ca2+, acts on PCT ( causes reabsorption of Ca2+ ) = INCREASES Ca2+ levels
Calcitonin is released from thyroid gland to DECREASE ca2+ levels
how does osteoporosis occur
how does oestrogen affect this
(10)
osteoclast activity > osteoblast activity
Osteoblast = builds bone =proliferation
RANK LIGAND =activates pre osteoClast
RANK ligand = signalling molecule, promotes differentiation , survival of preosteoclast, interacts with RANK-L receptor = activates it and causes bone loss !
Osteoprotegernin= protein that protects us from over reabsorption, by providing a decoy receptor for RANK ligand = so osteoclasts aren’t activated ( hence reducing bone loss )
Oestrogen increases bone reabsorption:
Oestrogen supresses RANK ligand signalling (to monitors the reabsorption and formation)
Also been shown to STOP the expression of osteoprogesterin , meaning bone reapsorbtion is out of control ! loss of bone occurs
how do we diagnose osteoporosis scan wise ?
2
1- DXA scan = bone miner density scan = T score will be less Than -2.5
Normal = x>-1
what does RANK-L do ?
2
RANK ligand = signalling molecule, promotes differentiation , survival of preosteoclast,
–> Interacts with RANK-L receptor on preosteoclast = activates it and causes bone loss !
what is osteoprotegerin ?
2
Osteoprotegerin= protein that protects us from over reabsorption,
-By providing a decoy receptor for RANK ligand = so osteoclasts aren’t activated ( hence reducing bone loss )
How can we treat osteoporosis ? (4) - 4 drugs - Disadvantages - Advantages how do they work CASE STUDY
Anti restorative Drug
1-Bisphospates (group)
pyrophosphate = inhibit osteoclast so they allow osteoblast more time to build stronger bone .
can cause :
-heart burn , flu like symptoms , osteonecrosis
2-Densosumab (1 drug)
Works against RANK-L = less activated osteoclast !
-given every 6 months
subcutaneous injection
-Bone gain can be lost when taken of treatment !
-hypocalaemia , infection , osteonecrosis
Anabolic drug:
3-Teriparatide
HUMAN Parathyroid hormone (increases ca2+ levels = stronger bone )
well tolerated
Other:
4-oestrogen and HRT ( less osteoclast activation )
Risk factors for osteoporosis ?
6
1- Smoking 2-Alcohol 3-Excersize 4-Ca2+ levels 5-Vit D 6-Very thin ( bones don't have much to carry so they turn off)
what is osteomalacia
what
how to treat
(2)
- bowed legs
= soft bones
give VIT D to treat well
Paggets disease?
3
what happens
investigations
treatments
1- Everything works way too fast = new bone is weak and prone to fracture
2-investigate = blood test for alkaline phosphatase = will be high
TREATMENT = bisphosponates
how do bisphosponates work + case study !
side effects
(4)
1-Bisphospates (group)
pyrophosphate = inhibit osteoclast so they allow osteoblast more time to build stronger bone .
can cause :
-heart burn , flu like symptoms , osteonecrosis
how does denosumab work ? - side effects (4) -when Is it given -cautions
2-Densosumab (1 drug)
Works against RANK-L = less activated osteoclast !
-given every 6 months
subcutaneous injection
-Bone gain can be lost when taken of treatment !
-hypocalaemia , infection , osteonecrosis
