Week 7 - Osteoporosis and Parathyroid Flashcards
What is osteoprosis
Thinning of the bone (low bone mass) and deterioration in bone archeticture
= more susceptible to fractures esp. hip, spine and wrist
How does osteoprosis occur
- ↓ osteoblasts activity
- ↑ osteoclasts actvity
- Low peak bone mass
- bone mass ↑ until reach approx. 25-30 then it peaks off before beginning to decline from age 40-50
- drops quicker in women due to menopause (sudden ↓ in oestrogen)
Bone is constantly turned over / remodelled
Whats the difference between osteblasts and osteoclast
OsteoBlasts - Build new Bone
Osteoclasts - break down old bone (reabsorbed) causing Calcium to be released into blood
Why is osteoporosis a healthcare concern in the UK
It is a growing healthcare problem
- affects 1 in 2 women and 1 in 5 men
AIM: ↓ risk of fracture
What factors can influence bone turnover
- Hormones
- Calcium and Vitamin D
- Weight bearing exercise
- Smoking
- Alcohol
- Medicines (esp. corticosteroids)
How does hormones affect bone turnover
inc. Oestrogen, Testosterone, Parathyroid, Calcitonin
- Oestrogen
- has protective effect on bone
- ↓ levels causes the rate of bone remodelling to ↑ and reabsortpion ↑ (more than bone formation)
- menopausal women
- Testosterone
- has protective effecxt on bone
- ↓ levels = ↑ osteoporosis risk
- Parathyroid hormone (PTH)
- PTH works on kidneys to conserve calcium
- stimulates calcitrol
- PTH stimulates osteoclasts = bone reabsorption / bone breakdowm stimulated = Ca2+ released into blood
- Calcitonin
- works on kidneys to excrete calcium (inihibts calcitrol)
List 6 risk factors for developing osteoporosis
- Smoking
- Alcohol (if drinking > 14 units a week)
- Low body weight
- Increasing age
- History of fracture / family history of fracture
- Female
- Oestrogen deficiency
- Use corticosteroids
- Low calcium intake
What lifestyle advice should be given to prevent and treat osteoporosis
What is the role of Bisphosphonates in managing Osteoprosis
1st Line Treatment = oral bisphosphonates
MUST take on EMPTY STOMACH or else bisphosphonates will bind to calcium in food
- need to swallow with water to prevent GI upset or irritation
Have weekly or daily preparations (have diff. licensing)
Check to see if drug is
Oral:
- need to ensure patient has adequate calcium and vitamin D intake
- Used in all patients (if menopausal HRT can be cosndiered too)
IV:
- only used if can’t tolerate oral or having adherence issues
Side Effects:
- GI upset
- Oesophageal irritation
What is the role of Strontium in managing Osteoprosis
2nd line
Used ONLY in POSTMENOPAUSAL women with NO CVD
Take at bedtime 2 hrs after food
- Has similar structure to calcium
- ↑ bone production (osteoblasts) + reduces reabsorption - Can be used separetly or added to bisphosphonate
What is the role of SERMs (raloxifene) in managing Osteoprosis
2nd line | SERM = selective oestrogen receptor modulator
Used ONLY in POSTMENOPAUSAL women with NO contraindications
Used in women unresponsive to bisphosphonates
CAN’T USE HRT alongside
- 2nd line
- Selective agonist (builds bone ~ osteoblast) + antagonist (reduce bone reabsorption ~ osteoclast) action on oestrogen receptors
What is the role of denosumab in managing Osteoprosis
3rd line | 2nd line in men
In men + post-menopausal women (with CVD / other contraindications)
Given as SC injection 2x a year
- Is a mAb which binds to receptor causing inhibition
- inhibtion blocks osteoclast action = stops bone being broken down + reabsorbed
-
What is the role of HRT in managing Osteoprosis
Synthetic PTH - ↑ intestinal absorption of Ca2+, ↑ reabsorption of Ca2+ and phosphates from kidneys
- a SC injection
- very expensive
- specialist use ONLY - have to refer to NICE guidelines
HRT - used to treat post-menopausal symtoms
What hormone is secreted from parathyroid gland + what is its role
(note: when have low levels of Ca2+)
PTH (parathyroid hormone)
-↑calcium + phosphate re-absorption in kidneys
-↑calcium absorption from intestines
- stimulates osteoclasts (bone reabsorption = Ca2+ is released)
What hormone is secreted from thyroid gland
(note: when have high Ca2+ levels)
Calcitonin
-↓ re-absorption of calcium + phosphates in kidney
-↓absorption of calcium in intestines / gut
- inhibits osteoclast activity
Has affects on kidney, gut and bones
NOTE: Calcitrol↑intestinal absorption of calcium
What is Calcitrol and its role
It is a hormone AND active form of vitamin D
- affects how much calcium is absorbed in gut
- vitamin D from food / produced from sunlight needs to be hydroxylated in both the liver and kidneys
- if have severe renal or hepatic impairment can become vitamin D deficient (no hydroxylation would occur)
- causes imbalance in calcium homeostasis = osteoporosis
How does lifestyle factors (i.e. smoking, alcohol and exercise) effect bone turnover
- Smoking
- nicotine inhibits osteoblasts
- inhibits intestinal absorption + kidney reabsorption
- induces enzymes = ↓PTH and oestrogen
- women who smoke experience earlier menopause
- ↓appetite = weight loss = low bone mass = ↑ risk - Alcohol
- inhibits osteoblasts
- impairs parathyroid gland = no PTH secreted in response to low Ca2+ levels of - Exercise
- puts mechanical stress on bone
- if obese less risk of osteoporosis as muscles grow to support weight = less likely to fracture
How does some medicines (e.g. corticosteroids) affect bone turnover
They↓ bone density =↑risk of osteoporosis
- Corticosteroids
- BIGGEST PROBLEM
- inhibits osteoblasts + stimulates osteoclasts
= reabsorption / break down of bone is more than building new bone
- ↓intestinal absorption of calcium + ↑ calcium excretion via kidneys - Aromatase Inhibitors
- used in breast cancer, oestrogen blockers = bind to OR
- ↓oestrogen levels = no protective effects - Cytotoxics
- traditional chemo treatment kills sex steroid hormones / inhibits their production e.g. testosterone and oestrogen
- ↓protective effects - Heparin and warfarin
- inhibits osteoblasts
