Biochemical Disorders of Bone Flashcards
What characterizes osteoporosis?
reduced bone mineral density
increased porosity
What is bone mineral density of osteoporosis defined as in terms of standard deviations below the mean?
less than 2.5 standard deviations below the mean
What is bone mineral density of osteopenia defined as in terms of standard deviations below the mean?
between 1-2.5 standard deviations below the mean
When does loss of bone mineral density tend to occur?
30 yrs
Why do women tend to lose more bone mineral density after the menopause?
increase in osteoclastic bone resorption due to loss of protective effects of oestrogen
What are the two types of primary osteoporosis?
Type 1 = post menopausal
Type 2 = osteoporosis of old age
What are the added risk factors in type 2 osteoporosis?
sunlight exposure reduced, chronic disease, inactivity
What type of fractures tend to occur in type 1 osteoporosis?
colles fractures
vertebral insufficiency fractures
What type of fractures tend to occur in type 2 osteoporosis?
femoral neck fractures
vertebral fractures
What can osteoporosis occur secondary to?
alcohol abuse, steroid use, malnutrition, chronic disease eg CKD, malignancy, RA and endocrine disorders (Cushings, hyperthyroid, hyperparathyroid)
How is osteoporosis diagnosed?
DEXA scanning
What happens to serum calcium and phosphate in osteoporosis?
are normal
Can any treatment s increase BMD?
no
What is the mainstay of treatment in osteoporosis?
slow any further deterioration/decrease fracture risk
How can peak bone mineral density be built up?
exercise, healthy lifestyle
What treatments are used to try to prevent fractures?
calcium and vit D supplements, bisphosphonates, Desunomab and strontium
What do bisphosphonates do?
reduce osteoclastic resorption
What are examples of bisphosphonates?
end in ate eg alendronate
What does strontium do?
increases osteoblast replication and reduces resorption
Is HRT a first line agent for prevention of osteoporosis after menopause?
No but can be considered if side effects with other medications occur
What are risks of HRT?
increast breast cancer/endometrial cancer rates
DVT
Does raloxifene (oestrogen receptor modulator) have a risk of DVT?
yes
What currently have the greatest evidence for efficacy, cost effectiveness and low side effect profile in terms of osteoporosis treatment?
bisphosphonates
What is osteomalacia?
qualitative defect of bone with abnormal softening of bone
What are there inadequate amounts of in osteomalacia?
calcium and phosphorus
What is the same as osteomalacia?
rickets
What may cause hypophosphataemia (a cause of osteomalacia)?
re feeding syndrome, alcohol abuse, malabsorption, renal tubular acidosis
What may patients complain of in osteomalacia?
bone pain, deformities
What may radiographs show in osteomalacia?
pseudofractures aka Looser’s zones
What is serum bone biochemistry like in osteomalacia?
low calcium, low phosphate, high ALP
Treatment of osteomalacia?
vit D therapy with calcium and phosphate supplements
What is primary hyperparathyroidism due to?
benign adenoma, hyperplasia or perhaps malignant neoplasia
What does overproduction of PTH lead to?
hypercalcaemia
Symptoms and signs of hypercalcaemia?
fatigue, nausea, depression, polyuria, renal stones, osteoporosis etc etc
In hyperparathyroidism what happens to phosphate?
is normal or low
What is secondary hyperparathyroidism?
overproduction of PTH secondary to hypocalcaemia caused by vitamin D deficiency OR CKD
What is tertiary hyperparathyroidism?
patients with secondary hyperparathyroidism who develop an adenoma which will continue to produce PTH, usually CKD related
