Calcium, Phosphate and Magnesium Flashcards
What are the normal reference ranges for calcium, phosphate and magnesium?
Calcium - 2.1 - 2.6 mmol/L
Phosphate - 0.8- 1.4 mmol/L
Magnesium - 0.75 - 1.00 mmol/L
How must phosphate levels be measured?
In a fasted state as vary with meals
Where is the bodies calcium mainly found?
In the bone, this is a resevoir for if the body needs extra calcium
What are the forms of calcium in the blood and which one is measured?
It can either be in its free ionised for or bound to albumin (around 50/50)
The total calcium is measured so a hypoalbuminaemia can cause a reduction in calcium even through the physiologically important free calcium will remain the same.
What are the main regulatory hormones that influence calcium levels?
Parathyroid hormone and 1,25 - vitamin D.
Also affected by growth hormone, adrenal steroids and sex hormones
What are the three ways that calcium levels are increased by parathyroid hormones?
Increased osteoclast activity causes bone breakdown that releases calcium
Increased reabsorption in the kidneys coupled with increased phosphate excretion
Increased absorption in the GI tract (requires 1,25 vitamin D)
How can you differentiate between raised ALP from the liver or from the bone?
A raise with gamma GT implies a liver cause
What would cause raised bone specific ALP?
Refelcts osteoblasti activity so would be raised in processes such as osteomalacia, bone mets, hyperparathyroidism
What are the main causes of hypercalaemia?
Primary hyperparathyroidism
malignancy
Artefact
What are the three main forms of hyperparathyroidism?
Primary hyperparathyroidism - due to parathyroid adenoma
Secondary hyperparathyroidism - renal failure, vitamin D deficiency, drug induced
Tertiary hyperparathyroidism - due to prolonged secondary hyperparathyroidism
What are the acute and chronic findings in hyperparathyroidism?
Acute: -nocturia and polyuria -renal colic -Mental impairment Chronic: -Bone pain -Anorexia -Nausea and vomiting -Drowsiness
What are the causes and clinical findings of hypocalcaemia?
Causes: artefact, hypoalbuminaemia, renal failure, vit D deficiency
Findings: Tetany - muscle spasms, especially face
What are the main causes of hypophosphataemia?
Intracellular shifts from insulin, glucose or respiratory alkalosis
Decreased renal function
Decreased intestinal absorption
Intracellular phosphate loss from ketoacidosis
How does hypophophataemia present clinically?
Presents with muscle weakness, neurological symptoms
how does hyperphosphataemia present?
It causes hypocalcaemia as it forces it into tissues so will present with these features e.g. tetany
