The Skeleton And Metabolism Flashcards
Where is calcium if its not in the bones?
Vesicles or circulation
How much calcium does the GIT absorb daily?
1g/day
What do the parathyroid glands release?
Parathyroid hormone
What does parathyroid hormone release cause?
Increased bone resorption, increased calcium reabsorption, increased vitamin D3 formation and decreased phosphate reabsorption
How does parathyroid hormone cause increased bone resorption?
RANKL/OPG and stimulation of osteoblast differentiation
What does intermittent PTH treatment cause?
Anabolic (Increased bone mass)
What does continuous PTH treatment cause?
Catabolic (decreased bone mass)
What does vitamin D3 do?
Increases calcium reabsorption from the diet in the gut and decreases parathyroid secretion
What does the amount of total phosphate excreted daily equal?
Daily intake of phosphate
What type of cells are osteoblasts?
Endocrine cells
What does high serum phosphate stimulate in osteocytes?
FGF23 synthesis
What does FGF23 act to do?
Increase phosphate excretion in the kidney
What patients were found to have an activating mutation on the FGF23 gene?
Autosomal dominant hypophosphatemic rickets
What is metabolic bone disease?
A group of diseases causing reduced bone mass and strength due to chemical imbalance
What does metabolic bone disease cause?
Altered bone cell activity, rate of mineralisation or changes in the bone structure
What is osteomalacia?
Defective mineralisation of normally synthesised bone matrix
What are the two possible causes of osteomalacia?
Vitamin D3 deficiency or phosphate deficiency
What does oncogenic osteomalacia cause?
Mesenchymal tumours producing excess FGF23
What are the outcomes of osteomalacia?
Bone pain/tenderness, fracture, proximal weakness and bone deformity
How does osteomalacia present?
Bowed long bones, widening of growth plates, loosers zone fracture
What is a loosers zone fracture?
Fracture at one side of the bone at 90 decreases to the cortical zone
What does hyperparathyroidism cause?
hypercalcemia and hypophosphatemia
What is primary hyperparathyroidism caused by?
Parathyroid adenomas or chief cell hyperplasia
What is secondary hyperparathyroidism caused by?
Chronic renal deficiency or vitamin D deficiency
