Biochemical Disorders of Bone Flashcards
What is osteoporosis
A quantitative defect of bone characterised by reduced bone mineral density and increased porosity
What are the complications of osteoporosis
Increased risk of fractures
What is the WHO definition of osteoporosis
Bone mineral density less than 2.5 standard deviations below the mean peak value of young adults of the same race and sex
What is the WHO definition of osteopenia
Bone mineral density if between 1 to 2.5 standard deviations below mean peak value
What are the two types of primary osteoporosis?
Post menopausal
Old age
What is post menopausal OP
exacerbated loss of bone in the post menopausal period- smoking, alcohol, lack of exercise and poor diet are further risk factors
What type of fractures tend to occur in post menopausal Op
colles fracture
vertebral insufficiency fracture
What is osteoporosis of old age
greater decline in bone mineral density than expected
What are the risk factors for old age OP
similar to type 1
chronic disease
Reduced sunlight exposure
Inactivity
What type of fracture predominate in old age OP
femoral neck
vertebral fractures
What conditions can osteoporosis be secondary to
Steroid use Alchohol Malnutrition Chronic disease Endocrine disorders eg cushings
How is osteoporosis diagnosised
DEXA bone scan
Which treatment for osteoporosis has the greatest evidence for efficacy
Biphosphonates eg alendronate, risedronate and etidronate
What is osteomalacia?
A qualitative defect of bone with abnormal softening of the bone due to deficient mineralization of osteoid (immature bones) secondary to inadequate amounts of calcium and phosphorus
What is rickets
Osteomalacia occurring in children which has subsequent effects on the growing skeleton
What is the principal cause of osteomalacia or rickets
Insufficient calcium absorption
A deficiency of or resistance to the action of vitamin D
Phosphate deficiency caused by increased renal loses
What are the symptoms of hypocalcaemia
Parasthesia Muscle cramps Irritability Fatigue Seizures Brittle nails
What are Looser’s xzones and where do they commonly occur
Pseudofractures particularly of the pubic rami, promixmal femora, ulna and ribs
What is the serium bone biochemistry in osteomalacia
low calcium
low phosphare
high serum alkaline phosphatase
How is the serium bone biochemistry different in osteoporosis compared to osteomalacia
Serium calcium and phosphate is normal in osteoporosis
What is the treatment of osteomalacia
Vitamen D therapy with calcium and phosphate supplementation
What is paget’s disease?
A chronic disorder which results in thickened brittle and mis-shapen bones
How do bones thicken in pagets
Increased osteoclast activity results in increased bone turnover
What is the new bone like In pagets
It is brittle and fractures easily- despite thickening the bew bone turnover is too fast and so new bone fail to remodel sufficiently
Where does pagets affect
the pelvis femur skull tibia ear ossicles - conductive deafness
What are the complications of pagets
arthritis fractures deformity pain high output cardiac failure
What is the biochemical picture in pagets
Serum alkaline phosphatase is raised whilst calcoim and phosphorum are normal
What is the treatment of Paget;s
bisphosphonates (inhibit osteoclasts)
Calcitonin
What is renal osteodystrophy
the bone changes that occur due to Chronic kidney disease
How can chronic kidney disease result in osteomalacia
reduced phosphate excretion and inactive activation of vitamin D result in secondary hyperparathyroidism with subsequent osteomalacia
