Calcium, Phosphate And Magnesium Flashcards
What are the 2 ways of absorption of calcium and magenesium in the intestine
Paracellular
Transcellular
In the kidney where is calcium, phosphtate and magnesium absorbed more
Calcium: pct and dct
Phosphate: pct
Magnesium: dct
What are the causes of hypocalcaemia
Chronic and acute renal fialure Vitamin d deficiency Hypo parathyroidism Acute pancreatitis Magnesium deficiency
What is the homesotasis of calcium and phosphate when there is low calcium
- Low calcium causes the release of PTH from the parathyroid gland
- PTH acts on the bone so calcium and phosphate is released
- There is also increased reabsorpion of calicum and decreased phosphate reabsorption in the kidney
- Pth acts on the kidney to stimulate the kidney to produce 1alpha OHase that converts 25OHD3 to 1,25OH2D3 ie vitamind D
- VitD acts on the bone to increase bone resorption so calcium is released
- Vitamind acts on the gut to cause calcium and phosphate absorption
- Vitamin d causes bone to regenerate FGF23 thaty causes decrease phosphate reabsorption so phosphate is secreted and calcium is corrected
- Vitamind d and corrected calcium sends a feedback to the parathyroid gland for negative feedback
What is the cause of rickets/osteomalacia
Vitamin d deficiency
What happens to the bone in osteomalacia/rickets
Lack of mineralisation of the bone due to failure of absorption of calcium from the GIT
What are the causes of vitamind deficiency
Imapired avaialblity of vitamind: lack of sunlight or fat malabsorptive state
Impaired liver hydroxyaltion
Impaired renal hydrocxyaltion to 1.25ohd
End organ insensitivity to vitamind metabolites
What is the treatment of osteomalacia/rickets
Vitamin d replacement
What happens when there is hypercalcaemia
Parathryoid gland causes a decrease in PTH
Bon resorption decreases
In the kidney: there is a decrease in phosphate excretion, increased calcium excretion. Reduced 1,25d3,
In the intestine: decreased calciuma and phosphatte absorption
All together this reduced serum calcium
What are the main causes of hypercalcaemia
Primary hyperparathyroidism - increased PTH
What are the 2 types of hyperparathyroidisim
Primary
Secondary
Tertiary
What is primary hyperparathyroidism
Increased PTH by adenoma, parathyroid hyperplasia and prathyroid carcinoma
What is secondary hyperparathyroidism
Due to:
Renal failure: failure of 1 hydroxylation
Vitamin d deficiency: failure to absorb calcium
Therefore PTH secretion increases
What is tertiary hyperparathyrodism
Prolonged secondary hyper parathyroidism
What are the symptoms of parathyroidism
Thirst, polyuria, constipation Aches and pains Lethargy and depression Confusion Renal stone, osteoporosis and pancreatitis
