[W2] Calcium, Phosphate and Magnesium Metabolism Flashcards
(28 cards)
Where is most calcium stored in the body?
99% in bone, 1% intracellular, 0.1% extracellular (mostly bound to albumin).
Name 3 functions of calcium.
- Clotting
- Muscle contraction
- Bone growth/remodelling
What is the reference range for adjusted calcium?
2.20–2.60 mmol/L.
How is adjusted calcium calculated?
Adjusted Ca = Measured Ca + ((40 - Albumin) × 0.02).
Where is phosphate primarily found?
85% bone, 14% in cells, 1% in blood.
Name 3 functions of phosphate.
- ATP formation
- Bone mineralisation
- Nucleic acid synthesis
What is the adult reference range for phosphate?
0.8–1.5 mmol/L.
Name 3 functions of magnesium.
- Enzyme cofactor
- Neuromuscular excitability
- ATP utilisation
What is the adult reference range for magnesium?
0.7–1.0 mmol/L.
Which major hormones regulate calcium and phosphate?
- Parathyroid hormone (PTH)
- Vitamin D
What is the function of PTH?
Increases bone resorption, Ca²⁺ reabsorption in kidneys, activates vitamin D, and promotes phosphate excretion.
What is the role of vitamin D?
Enhances intestinal absorption of Ca²⁺ and phosphate, regulates bone metabolism, and inhibits PTH.
What are the symptoms of hypercalcaemia?
“Bones, stones, moans, groans” + arrhythmias, renal damage.
What are causes of hypercalcaemia with ↓PTH?
- Malignancy
- Sarcoidosis
- Vitamin D toxicity
What are the symptoms of hypocalcaemia?
Neuromuscular excitability, tetany, Chvostek’s and Trousseau’s signs.
What are causes of hypocalcaemia with ↑PTH?
- Vitamin D deficiency
- Renal failure
- Pancreatitis
What are the symptoms of hyperphosphataemia?
Hypocalcaemia (acute), soft tissue calcification (chronic).
What are causes of hypophosphataemia?
- Refeeding syndrome
- Malabsorption
- Hyperparathyroidism
What are the symptoms of hypermagnesaemia?
ECG changes, respiratory paralysis, cardiac arrest.
What are causes of hypomagnesaemia?
- GI loss
- Alcoholism
- Diuretics
- PPIs
- Refeeding syndrome
Name the main bone cell types.
- Osteoblasts (form bone)
- Osteoclasts (resorb bone)
- Osteocytes (maintain)
- Osteogenic cells (stem cells)
What is osteoporosis?
Low bone mass and deterioration, diagnosed by DEXA (T-score ≤ –2.5).
What is osteomalacia/rickets?
Due to vitamin D/phosphate deficiency; results in soft bones.
What is Paget’s disease?
Focal bone disorder causing disorganised bone remodelling.
