Metabolic Bone Disorders: Osteoporosis Flashcards
What is osteoporosis
Low bone mass and derivation of microarchitecture of bone tissue (loss of spongy bone)
What is the most common complication of osteoporosis
Hip fractures
Fracture of wrists, vertebrate and humerus
How is osteoporosis classified
T score- number of standard deviations that a patients bone mass measurement is from
Normal:
T score > -1
Osteopoenia:
T score -1 to -2.5
Osteoporosis:
T score below -2.5
Established osteoporosis
T score
What are the risk factors of osteoporosis
Age- 50
Gender- most case it is women
Slight build, low BMI
Untreated premature menopause
Prolonged amenorrhoea
Male hypogondaism
ALCOHOL
Smoking
Corticosteroid use
Family history- mothers side of the family with hip fracture
Other conditions-
Inflammatory bowel or coeliac disease
Hyperthyroidism
Renal failure
How do you prevent osteoporosis
Lifestyle modification:
Regular weight bearing exercise
Stopping smoking before menopause
Maintain adequate levels of calcium and vitamin D (700mg per day)
Reduce alcohol consumption
Maintain BMI >19kg/m2
How do you diagnose osteoporosis
DEXA scan- Dual Energy Xray Absorptionmetry
(low energy x rays penetrate less dense bone better)
Previous fracture and over 75
When do you take a patient in for a DEXA scan
previous fracture and over 75
Risk factors of osteoporosis
Osteopenia x ray done
Long term steroid use with calcium and vitamin D supplements and over 65
What is the first line treatment option available for osteoporosis and give an example of it
BISPHOSPHONATES
Example:
ALDEDRONIC ACID
RISEDRONATE SODIUM
What other treatment options other than the first line is available for osteoporosis
Hormone replacement therapy for over 50’s
RALOXIFENE- selective oestrogen receptor modulator
Strontium Ranelate- over 75 years with previous condition and low BMD (bone mineral density)
Use of calcitonin
Teriparatide over 65 years (Low BMD)
What is the role and mechanism of action of bisphosphonates
Enzyme resistant analogue of pyrophosphate that inhibits bone reabsorption
50% binds at sites of bone mineralisation where they stop the osteoclasts from breaking down the bone (they are ingested instead of bone by osteoclasts)
What are the side effects of bisphosphonates
Gastrointestinal side effects
Severe oesophageal reaction and stricture
What should you avoid when taking bisphosphonates and what reduces its absorption (drug wise)
Do not take at bed time
Avoid food before and after dose as it impairs absorption- at least 30 minutes
Antacids, calcium salts and iron reduce absorption
What is found in patients given bisphosphonates via IV
Osteonecrosis of jaws- death of jawbone
What is the dose of bisphosphonates in men and women
Women: 10mg or 70mg ONCE daily
Men: 10mg ONCE daily
What is found in hormone replacement therapy, its role and the risk
Oestrogen
Role:
Maintenance of bone integrity by inhibition of cytokines which recruit osteoclasts and opposing bones reabsorption (Ca2+)
Risk: cancer
Give an example of a selective oestrogen receptor modulator (SERM), role of action and the risk
RALOXIFENE
Selective agonist activity on bone and cardiovascular system and antagonist activity on mammary tissue and uterus
Risk: increased risk of venous thromboembolism
When can strontium ranelate be used and its mechanism of action
Post menopausal osteoporosis or women with high risk fracture (over 75 years)
Inhibition of bone reabsorption
through being adsorbed into hydroxyapatite crystals in bone in exchange for Ca2+ in mineralised bone
What is the mechanism of action of calcitonin and its role
Maintaining calcium homeostasis and bone
MoA:
Inhibition of osteoclast action directly via specific receptors
Decreases plasma Ca2+ and decreases reabsorption of Ca2+ and phosphate in kidney
What is role of PTH (parathyroid hormone)
Increases osteoclast number
Stimulates their activity
Increases bone mass, integrity and strength
Decrease in osteoblast apoptosis
Give an example of PTH
Teriparatide
What are the two different types of corticosteroids and what biomarkers do they imitate in the body
Glucocorticoids- cortisol
Mineralocorticoids- aldosterone
How do corticosteroids induce osteoporosis
Use of excessive pharmacological concentrations inhibits bone formation by inhibiting OSTEOBLASTS
Also may stimulate OSTEOCLAST action
How do you reduce risk of corticosteroid induced osteoporosis
DOSE: Low as possible and shortest course of treatment
Take calcium or vitamin D supplements
What is Calcitriol
Vitamin D3 analogue
What is Paget’s disease of bone
Areas of bone undergoing accelerated bone remodelling due to hyperactivity of osteoblasts and osteoclasts
Bones enlarge, become structurally abnormal and weaker than normal
What are the symptoms of Paget’s disease
Bone aching- worse at rest or night
Bone enlargement: skull, spine and pelvis
Deformity
Changes in adjacent joint structure leading to osteoarthritis (wear and tear)
Hypercalcaemia:
Increased hypertension, kidney stones, muscle weakness
Increased blood flow- heart failure
How do you treat paget’s disease
Bisphosphonates:
Risedronate sodium- 30mg daily for 2 months
Calcitonin: 50 units THREE times a week
NSAIDS for pain
How does rickets occur in children
Lack of sunlight exposure
Lack of vitamin D in diet
How does Osteomalacia occur in adults
Vitamin D deficiency
What can vitamin D deficiency lead to
Decreased plasma calcium and phosphate levels (impacts bone)
Increased plasma Ca2+ levels lead to PTH levels increasing and depletion of calcium stores in bone (soft weak bone)
What is the role of vitamin D
Maintaining plasma Ca2+ by increasing absorption in intestine and kidney
Mobilising it from bone- increase osteoclast maturation and activity (decrease renal excretion)
Decreases osteoblast synthesis in collagen
What are the two forms of vitamin D and where can they be obtained
Vitamin D2- diet
Vitamin D3- colecalcifediol- sunlight
What does low vitamin D means for the body in calcium homeostasis
- Low blood Ca2+ levels
- Stimulates PTH secretion
- PTH acts on kidney, large intestine, bone to increase blood Ca2+
- Increased blood Ca2+
What are the symptoms of osteomalacia and rickets
Bone pain and tenderness
Skeletal deformity:
Bow legs
Pigeon Chest
Spinal deformity
Dental deformities
Muscular problems- weakness, cramps
Impaired growth
Low calcium- hands and feet spasms
What are the causes of osteomalacia or rickets
Dietary deficiency- dark skin living in northern climates
Age related- vitamin D metabolism decreases with age
Secondary rickets/osteomalacia- liver disease or renal failure
Vitamin D dependent rickets- decreased renal absorption of phosphate
How do you treat rickets or osteomalacia
Calcium and vitamin D supplements
