Bones Flashcards
Factors that increase calcium (2)
PTH
Calcitriol (activated vitamin D)(1,25-(OH)2D3)
Factors that decrease calcium
Calcitonin
Where is calcitonin synthesised
parafollicular cells
Describe the synthesis of calcitriol
Vitamin D from diet and UV light
25 hydroxylase in the liver converts it to 25-hydroxyD3
1alpha hydroxylase and PTH in the kidneys convert it to calcitriol
Where does PTH have its effects
Kidneys
Bone
Small intestines
Where does calcitriol have its effects
Kidneys
Bone
Small intestines
Effect of PTH in the kidneys (3)
1α-hydroxylase stimulation
Increased calcium reabsorption
Increased phosphate excretion
Effect of PTH in the bone
Increased bone resorption
Effect of PTH in the small intestines (2)
Increased calcium absorption
Increased phosphate absorption
Effect of calcitriol in the kidneys (2)
Increased calcium reabsorption
Decreased phosphate reabsorption
Effect of calcitriol in bone
Increased bone formation
Effect of calcitriol in the small intestines (2)
Increased calcium absorption
Increased phosphate absorption
Resultant effect of PTH
↑ Calcium
↓ Phosphate
Resultant effect of calcitriol
↑ ↑ Calcium
↓ Phosphate
- Which hormone decreases blood calcium levels?
Calcitonin
- Which hormone, out of PTH and calcitriol, raises blood calcium levels the most?
Calcitriol
- Which enzyme does PTH activate in the kidneys?
1α-hydroxylase
- What does PTH do to your blood phosphate levels?
Decreases
- Why may the UK population be generally vitamin D deficient?
Less sunlight (UV)
What decreases PTH production
Calcitriol and increased calcium
What happens in primary hyperparathyroidism
Autonomous secretion of PTH uninhibited by calcium
What happens in secondary hyperparathyroidism
Physiological response to hypocalcaemia
Signs of hypocalcaemia (4)
CATs go numb
Convulsions
Arrhythmias (e.g. prolonged QT interval)
Tetany
Paraesthesia (hands, mouth, feet, lips)
What are the signs you can elicit in hypocalcaemia (2)
Trousseau’s sign
Chvostek’s sign