Calcium And Phosphate Flashcards
What is the acronym for the uses of Calcium?
MISBEN
Where does Parathyroid Hormone act?
Kidneys and Bone
What effect does PTH have on bone?
Increase Ca2+ resorption
Increase PO4 3- resorption
What effect does PTH have on the Kidneys? (2)
- Increase Ca2+ reabsorption, decrease PO4 3- reabsorption
2. Secretion of 1α hydroxylase
Where is 90% of vitamin D in the body from?
The sun, absorbed through skin as D3
Where is 10% of the Vitamin D in the body from?
Diet, in D2 form
What effect does the liver have on vitamin D?
Secretes 25 hydroxylase to convert it to Calcidiol
What effect do the kidneys have on vitamin D?
Secrete 1α hydroxylase (stimulated by PTH) to convert it to Calcitriol (active Vitamin D)
Where does Calcitriol (active Vitamin D) affect?
Kidneys, Bone, Gut
What does Calcitriol do to the kidneys?
Increase reabsorption of Ca2+ and PO4 3-
What effect does Calcitriol have on Bone?
Increase Ca2+ and PO4 3- resorption
What effect does Calcitriol have on the gut?
Increase Ca2+ absorption, increase PO4 3- absorption
Where is Calcitonin produced?
C cells of the Thyroid gland
What stimulates production of Calcitonin?
Increasing serum levels of Ca2+
What stimulates production of PTH?
Decreasing levels of plasma Ca2+
What effects does Calcitonin have?
Blocks effects of PTH:
Kidneys - decrease Ca2+, increase PO4 3- absorption; decrease 1α hydroxylase secretion
Bone - decrease Ca2+ and PO4 3- resorption
Name the 6 uses of Calcium
Muscle Contraction Intracellular signalling Stabilise membrane potential Bones + teeth Enzyme Cofactor Nerve function/Neurotransmission
Where is most Calcium stored in the body?
Bones (99%)
Where is the remaining body calcium found?
Intracellular (~1%) and Extracellular (plasma - ~01.%)
What is Parathyroid Hormone-Related Peptide (PTHrP)?
Hormone that mimics PTH: produced by some cancers, and causes hypercalcaemia associated with malignancy
NB: does not increase 1,25 D3 levels
What is FGF-23?
Fibroblast Growth Factor.
Predominantly made by osteocytes and osteoblasts
What does FGF-23 do?
Prevents vitamin D mediated hyperphosphataemia by increasing removal via urine (phosphaturic)
Inhibits 1α hydroxylase -> decreases active levels of Vitamin D
Inhibits type II sodium phosphate co-transporters
What are the symptoms of Hypocalcaemia?
Neuromuscular irritability
Muscle Cramps / Tetany
Seizures
Why does Tetany occur in hypocalcaemia?
As extracellular Ca2+ falls, peripheral nerve fibres discharge spontaneously, leading to muscle contractions
What are the symptoms of Hypercalcaemia?
Nausea/vomiting/constipation/anorexia Tiredness, confusion, depression, headaches Muscle weakness Kidney stones Loss of bone Polyuria
What can cause hypercalcaemia?
Primary or Tertiary Hyperparathyroidism
What can cause Hypocalcaemia?
Primary and Pseudo- Hypoparathyroidism, and Secondary Hyperparathyroidism
What is the treatment of Hypercalcaemia?
Fluids
Loop diuretic (e.g. Furosemide)
Calcitonin
Bisphosphonates
What is the treatment for Hypocalcaemia?
Acute: IV calcium gluconate
Chronic: oral calcium + vitamin D
What is the principle of management for hypo/hypercalcaemia?
Aim to restore normal Ca levels, treat any emergency symptoms, and find underlying cause
