Metabolic bone disease Flashcards
How do we describe calcium that is bound to albumin?
Inactive
How much calcium in urine per day?
0.2g/day (same amount that is gained in the intestine)
what fraction of the ca we eat gets absorbed?
1/5
What percentage of Ca is reabsorbed from the glomerular filtrate?
98%
What mass of calcium per day is engaged in bone turnover?
0.5g (more in growing person or if preggas)
Where do we get Vitamin D3 from?
Fish, meat
Where vit D2 from?
Vitamin supplements
why is sunlight needed in vitamin D metabolism>
Needed to convert 7-dehydrocholesterol into vitamin d3
Which hormone maintains calcium balance in the body?
PTH (parathyroid hormone) - low serum calcium means PTH secretion increased.
How many parathyroid glands is there?
4
What does PTH do?
Stimulates the enzyme that activates vitamin D, which increases calcitriol production from kidney and decreases calcium excretion.
Radioisotope scanning - what can this highlight?
Fracture, bone infection, cancerous deposit
What does dual energy X ray absorpitometry assess? (DEXA)
Bone mineral density - can be used to diagnose osteoporosis.
What is PRIMARY hyperparathyroidism?
Excessive PTH secretion resulting in hypercalcaemia.
What is SECONDARY parathyroidism?
PTH above normal level but APPROPRIATE (calcium is low), PTH should be higher to raise the low level of calcium.
4 reasons why someone may be vitamin D deficient?
Lack of sunlight, dietary lack, malabsorption, impaired activation - renal failure.
3 causes of rickets?
Phosphaturia and low Ca intake
what is tetany?
muscle spasms due to low calcium in bones
2 activated forms of vitamin D you can give?
Alfacalcidol or calcitriol (given in kidney disease)
Effects of Pagets disease?
Deafness, uncoordinated bone remodelling, pain, nerve compression, bones more likely to fracture
Treatment of pagets?
bisphosphonates, - they inhibit osteoclasts (all end in ate)
T score in osteoporosis?
-2.5 or lower
Treatment of osteoporosis?
Low dose bisphosphonates, HRT, Ca and D3, Denosumab, PTH injections
what can a high dose of bisphosphonates cause?
Bisphosphonate related osteonecrosis of the jaw
common sites of bone mestastases
great lung and prostate
Myeloma?
malignancy of plasma cells in bone marrow
what is vitamin D3 stored as in the liver
25-vitd3
what is alkaline phosphatase associated with?
osteoblasts
when are Beta crosslaps levels used
post menopausal women
difference between pagets and osteoporosis
pagets is more localised
osteonecrosis of the jaw key drug
denosumab
