Calcium and Bone Tutorial Flashcards
what nakes up bone
collagen (protein) calcium phosphate
what are the component forms of bone
trabecular - porous sponge like
cortical bone- dense, forms outside of bones
what is the mineral that adds strength to bones
calcium phosphate
what hormones regulate calcium
parathyroid hormone
calcitonin - a polypeptide
vitamin D - from diet and sunlight
what does the parathyroid gland sense in relation to calcium
senses calcium levels via calcium sensing receptors
what secretes calcitonin
parafollicular C cell within the thryoid gland
where is vitamin D activated
by enzymes within the liver and kidneys
what is the role of calcium
maintaining bone strength
excitability of smooth and cardiac muscle
secretion of peptides and hormones in the body
excitability of skeletal neuromuscular junctions
role in blood clotting
what is the primary controller of calcium levels in the body
parathyroid hormone
what stimulates PTH
hypocalcaemia
what is the function of PTH
increase serum calcium and phosphate
activates vit D within the kidney
what is the action of PTH on bone
increases osteoclast activity within bones causing increased resorption of bone and calcium to be released
what is PTHs action on the kidney
increased tubular resorption of calcium, increasing serum levels
increases the excretion of phosphate in urine
what is the active for of vitamin D
1,25 di-OH cholecalciferol
what is the role of vitamin D
maintains mineralisation of bone in the body
helps absorption of Ca2+ and PO43 in the intestines
when is calcitonin released
in extreme cases of hypercalcaemia
what is the role of calcitonin
decreases serum calcium within the body
what effect does deficiency or excess of calcitonin have on bone health
none
how does calcitonin work
inhibits osteoclasts, decreasing bone resorption and lowering serum calcium
lowers levels of calcium and PO43- by decreasing absorption in the intestines
decreases resorption within the kidneys - Ca2+ and PO43- is excreted in urine
increased calcium movement from plasma to bone
what are the consequences of hypercalcaemia
stones, bones, moans and abdominal groans:
- increased stimulation of smooth muscles, nerves and the heart
- tiredness, confusion, depression
- kidney stones
- arrhythmias
- muscle weakness
- constipation
what are the consequences of hypocalcaemia
increased excitability of skeletal muscle- tetany of muscles, cramps
pins and needles in hands, feet and lips
contraction of respiratory muscles - asphyxiation
what results from hyperparathyroidism
hypercalcaemia increased activity of osteoclasts osteoporosis - fractures low serum phosphate levels due to reabsorption of calcium in kidneys renal stones
what are the subtypes of hyperparathyroidism
primary, secondary and tertiary
what is primary hyperparathyroidism caused by
overactivity of parathyroidgland
what is secondary hyperparathyroidism caused by
physiological response to low calcium (PTH raised, calcium low)
what is tertiary hyperparathyroidism caused by
parathyroid gland becomes autonomous after many years of secondary
what can diagnose primary hypercalcaemia (the most common cause)
raised serum calcium
raised serum PTH
increased urine calcium excretion
what is the treatment for hyperparathyroidism
surgery to remove adenoma causing hypersecretion (only if patient has renal stones, renal impairment or severe osteoporosis)
high fluid intake
avoid vit D and calcium high diet
what causes hypoparathyroidism
lack of cells within the parathyroid gland that can secrete PTH
- de george = congenital absence of PT glands
- destruction via malignancies
- autoimmune disease- destruction of parafollicular cells
what will be seen in blood serums for hypoparathyroidism
hypocalcaemia and hyperphosphataemia
what are the signs of hypoparathryoidism
signs of hypocalcaemia:
-chvostek sign (twitching of the face muscle when face nerve gently tapped)
-trousseaus sign- inflammation of the blood pressure cuff over systolic will cause tetany of the muscles in the hand and wrist
although increased bone calcium and density fractures still high as abnormal
what would serum levels in hypoparathyroidism be like
decreased PTH
decreased calcium
increased PO43-
what is the treatment for hypoparathyroidism
calcium and vitamin D supplements
what causes pseudohypoparathyroidism
genetic receptor abnormality leading to resistance of the PTH hormone in the body
what are serum levels like in pseudohypoparathyroidism
high PTH
decreased calcium
increased PO43-
what are the complications of pseudohypoparathyroidism
subcutaneous calcification mental retardation blunting of the 4th metacarpal obesity bone abnormalities
what can cause lack of vit D
lack of sunlight absorption (winter months, skin pigment, not outdoors enough) lack of absorption of the prehormone- poor diet, malabsorption (coeliac) liver failure (stops activation)
what does lack of vitamin D do
decreases Ca2+ and PO4s absorption within the intestine
PTH secretion will be increased as a result
lack of bone mineralisation
what are the complications of vit d deficiency
rickets and craniotabes (tenderness of the skull presents as neonatal rickets) and widened epiphyses at the wrists and abnormalities in the costochondral joints (these all in children)
in adults: osteomalacia- due to lack of mineralisation bones soften becoming more likely to fracture. will have bone and muscle pain. gait deformities may occur due to proximal myopathy
