Hyperphosphatemia/Hypophosphatemia Flashcards
Hyperphosthatemia
high phosphate levels in the blood
Function
- 85% in bones
- combines with calcium to form hydroxyapatite - makes bones hard - 1% EXTRACELLULAR
- 14% INTRACELLULAR
• phosphorylation
• ATP
• Part of DNA/RNA
Phosphate and calcium
Calcium and phosphate in the blood are bound togather
- If Calcium levels fall
- Parathyroid hormone is released
- This hormone frees up both Calcium and phosphate from the bones
Causes of hyperphosphatemia
( ASSOC W PARATHYROID/CALCIUM(
- Acute/chronic kidney disease - gfr falls thus less excretion means more phosphate build up
- Kidneys unable to reabsorb calcium so more gets excreted
- > parathyroid hormone is released by gland
- > Secondary parathyroidism
- > Increased release of phosphate and calcium ions
- > Renal osteodystrophy - bones become weak and thin in people with chronic kidney disease - Pseudohypoparathyroidism - receptors do not respond to parathyroid hormone due to genetic defect
- > Calcium gets lost and phosphate build up instead
- > Same pattern as in kidney disease - Hypoparathyroidism
Causes of Hyperphosphatemia
( Excess build up in blood)
- Excessive intake and absorbtion in GI tract
- Mass cell apoptosis
- > causes release of intracelllular phosophate - Respiratory acidosis
• co2 levels rise as a result of drop in ventilation
• CO2 diffuses into cell to react and form carbonic acid
• Lowers cellular Ph as it gets more acidic
• Lower pH inhibits glycolysis
• Less phosphate pulled out of the blood
•Phosphate levels in the blood rise - Diabetic ketacidosis
• Low insulin in blood
• Cells extract less phosphate from the blood ( mech unclear)
• Phosphate builds up
Symptoms
Mild cases -> no symptoms
Severe cases
1. Neurons become more excitable
• Spontaneous firing -> Tetany (involuntary muscle contraction)
• Causes Chvostek’s sign / Trousseau’s sign
2. Tingling around the mouth
3. Seizures
- Bone pain
- Bone like crystals/under skin/blood vessel walls/joints/ - excess phosphate finds and binds to calcium
• Nephrocalcinosis - long term calcification of kidney
Diagnosis
Phosphate levels above 4.5 mg/dl
Treatment
• Decreased intake - avoid food with a lot of phosphate
• Medication - phosphate binders
- Increase excretion of phosphate - intravenous fluids/ loop diuretics
Hypophosphataemia
low phosphate levels in the blood
Hypophosphataemia causes
EXCESS PO4- lost
• Primary hyperparathyroidism - too much parathyroid hormone release
- Excess phosphate is lost in the urine as it inhibits PO4 uptake
• Fanconi Syndrome
- Proximal convulated tubule lose capacity to reabsorb variety of solutes including phosphate
- excess secreted in urine
Hypophosphataemia causes
not enough absorbed in the GI tract
- Alcohol - impairs absorbtion
2. Medication - antacids contain AL, Ca, Mg bind to negative Phosphate ion and block absorbtion
Hypophosphataemia
not enough in the diet/Excess extraction from blood
• Malnourishment /Anorexia nervosa
- blood glucose is low and cellular metabolism slows down considerably
- Refeeding syndrome - when nourishment is recieved, phosphate ions are rapidly taken up for ATP production leaving v little in blood
- Risk of arrythmias and neurological problems
• Diabetes - not enough insulin in produced
- diabetic ketoacidosis developed
- insulin causes extraction of phosphate from blood
- phosphate levels fall
• Respiratory Alkalosis
- increased PH inside cell
- Glycolysis stimulated - this process requires alot of phosphate
- Pull excess phosphate out of blood
- Hypophosphataemia
Symptoms of hypophosphataemia
Severe • Muscle weakness • Osteomalacia - weak bones • Rhabdomylosis - kidney damage due to muscle breakdown • Altered mental status • Hyper calcaemia symptoms
Symptoms of hypercalcaemia
- Stones - kidney stones
- Bones - pain pain from chronic demineralisation
- Thrones - polyuria
- Groans - constipation and muscle weakness
- Psychiatric overtones - depressed
Diagnosis of phosphate
• Blood levels below 2.5 mg/dl
