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Year 3: Medicine Block ENDOCRINOLOGY > Electrolytes: Calcium, Magnesium and Phosphate > Flashcards

Electrolytes: Calcium, Magnesium and Phosphate Flashcards

1
Q

What are the calcium compartments within the body?

A
  • 99% in bones – calcium hydroxyapatite
  • 0.99% - extracellular and interstitium
  • 0.01% - intracellular
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2
Q

How is Calcium transported within the body?

A
  • Into cells using ligand gated channels and voltage gated channels

​​​

  • Out of cell with NCX and ATP-Ca2+ pump
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3
Q

What are the types of Extracellular Ca2+?

A
  • Diffusible

​

  • Non-diffusible: large and bold to albumin
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4
Q

What are forms of Diffusible Calcium?

A
  • Free ionised: blood coagulation, hormone secretion, contraction of muscle, neuron action potentials
  • Calcium Oxalate: electrically neutral and not useful for cellular processes
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5
Q

How does pH affect non-diffusible calcium?

A
  • Acidosis increases protons bound to albumin which lead to increased free ionised Ca2+ extracellularly and less bound Ca2+ due to repelling of Ca2+ by postively charged albumin
  • Alkalosis decreases protons bound to albumin which lead to decrease free ionised Ca2+ extracellularly and more bound Ca2+ due to attractive of negatively charged albumin
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6
Q

How does concentration affect non-diffusible calcium?

A
  • Hyperalbuminemia increases amount of protein bound Ca2+. Same free ionised Ca2+. Pseudohypercalcaemia
  • Hypoalbuminaemia decrease amount of protein bound Ca2+. Same free ionised Ca2+. Pseudohypocalcaemia
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7
Q

How is Calcium regulated?

A
  • Changes in extracellular Ca2+ detected by calcium sensing receptor in parathyroid cells. Affect parathyroid hormone amount
  • Affects the kidneys, bones and GI active vitamin D to maintain or lose Ca2+
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8
Q

What are common causes of Hypercalcaemia?

A
  • Primary Hyperparathyroidism: commonest cause in non-hospitalised patients o Osteoclastic bone resorption
  • Malignancy: the commonest cause in hospitalised patients. This may be due to number of processes, including; bone metastases, myeloma, PTHrP from squamous cell lung cancer
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9
Q

What are other causes of Hypercalcaemia?

A
  • Drugs: thiazides, calcium containing antacids
  • Vitamin D intoxication
  • Sarcoidosis* (other granulomatous diseases as well)
  • Acromegaly
  • Thyrotoxicosis
  • Milk-alkali syndrome
  • Dehydration
  • Addison’s disease
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10
Q

What are symptoms of Hypercalcaemia?

A
  • (Bones, Stones, Groans and Psychic Moans)
    • Slower or absent reflexes
    • General muscle weakness
    • Polyuria, Polydipsia
    • Constipation
    • Abdominal Pain
    • Confusion
    • Hallucinations
    • Stupor, tiredness, weakness
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11
Q

What are some clinical syndromes caused as a result of Hypercalcaemia?

A
  • Calcium oxalate kidney stones due to hypercalciuria
  • Anorexia
  • Weight loss,
  • Hypertension
  • Ectopic Calcification
  • Cardiac Arrest
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12
Q

How is Hypercalcaemia investigated?

A
  • High Ca2+ in blood
  • Electrocardiogram showing Bradycardia and AV block. Osborne wave
  • Checking levels of PTH, Vit D, Phosphorus, Magnesium, Albumin
  • Malignancy: decreased albumin, decreased chloride, alkalosis, decreased potassium, increased phosphate,
  • Increased PTH indicates hyperparathyroidism
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13
Q

How is Hypercalcaemia managed?

A
  • Rehydration with 3 to 4 litres of IV 0.9% N saline.
  • Following this, bisphosphonates may be used.
  • Loop Diuretics can be used to inhibit Ca2+ absorption
  • Glucocorticoids to increase GI excretion
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14
Q

What are common causes of Hypocalcaemia?

A
  • Hypoparathyroidism
    • Surgical removal
    • Autoimmune destruction
    • Congenital problems e.g. DiGeorge syndrome
    • Deficiency in magnesium
  • Low Vitamin D
    • ​Deficient diet, Malabsorption
    • Cirrhosis
    • Lack of sunlight
    • Chronic renal failure
  • Kidney Failure
  • Tissue injury
    • Burns
    • Rhabdomyolysis
    • Tumour lysis syndrome: Due to increase phosphate release which form insoluble compounds with free ionised Calcium leading to calcium phosphate formation
  • Acute Pancreatitis
  • Blood transfusions
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15
Q

What are symptoms of Hypocalcaemia?

A
  • Tetany (unstable Na+ channels)
  • Muscle cramps
  • Abdominal pain
  • Periorbital tingling
  • Seizure, Anxious
  • Dermatitis
  • Perioral Paraesthesia
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16
Q

What are signs of Hypocalcaemia?

A
  • Chvostek’s sign
  • Trousseau’s sign
  • Laryngospasm
  • Cataract’s (chronic)
17
Q

How is Hypocalcaemia investigated?

A
  • Low Ca2+ in blood
  • Electrocardiogram showing prolonged ST and QT, Arrythmias such as Torsades de points and AF
  • Checking levels of PTH, Vit D, Phosphorus, Magnesium, Albumin
18
Q

How is Hypocalcaemia managed?

A
  • PO calcium in mild cases
  • Calcium Gluconate
  • Vitamin D supplementation
19
Q

What are the compartments of Phosphate within the body?

A
  • 85% in bones: combined with calcium to form calcium hydroxyapatiei
  • 1% extracellular
  • 14% intracellular: phosphorylation, ATP formation, part of DNA and RNA backbone, Part of Cell-Signalling Pathways
20
Q

How are Phosphates regulated?

A
  • Changes vary with calcium levels.
  • PTH can cause break down calcium hydroxyapatite to release Calcium and Phosphate ion which bind together again and Travel to kidney.
  • Phosphate usually reabsorbed by sodium-phosphate co-transporters but in presence of PTH, the reabsorption of phosphate is decreased and calcium increased.
  • Phosphate lost in urine and Calcium kept in blood.
21
Q

What are common causes Hyperphosphataemia?

A
  • Acute/Chronic kidney disease
    • Secondary hyperparathyroidism: Phosphate reabsorbed into blood due to impaired excretion
    • Pseudohypoparathyroidism: receptors don’t repond to PTH
  • Hypoparathyroidism
  • Excessive Intake
    • Phosphate based laxative intake
  • Cell death
    • Crush injury, tumour lysis syndrome, rhabdomyolysis
  • Metabolic
    • Respiratory acidosis decrease glycolysis so less phosphate drawn into cells
    • DKA reduces cell intake of phosphate
22
Q

What are symptoms of Hyperphophataeimia?

A
  • Tetany
  • Chvostek’s sign
  • Trosseau’s sign
  • Tingling around a mouth
  • Seizures
  • Bone pain
  • Metastatic Calcification e.g. nephrocalcinosis
23
Q

What is the investigations and management of Hyperphospataemia?

A

Blood tests are the main investigation

Management

  • Decrease intake
    • Avoid certain foods (dairy, meat, soda)
    • Medication (PO4)3- binders (sevelamer)
  • Increase excretion
    • Fluids
    • Loop diuretics
24
Q

What are common causes of Hypophosphatemia?

A
  • Primary Hyperparathyroidism
  • Vitamin D deficiency
  • Refeeding Syndrome
  • Fanconi Syndrome
  • Lack of Absorption through GI: alcohol, medications, antacids
  • Starvation e.g. malnourishment, anorexia nervosa
  • Respiratory alkalosis
25
Q

What are symptoms of Hypophosphataemia?

A
  • Muscle weakness
  • Osteomalacia
  • Rhabdomyolysis
  • Altered mental status
  • Symptoms of hypercalcaemia
  • Arrhythmias or cardiac arrest
  • Red cell, White cell and Platelet dysfunction
26
Q

What are the investigations and management of Hypophospataemia?

A

Blood tests is the investigation

Management

  • Intravenous or oral phosphate slowly (don’t give to patient who is hypercalcaemic or oliguric)
  • Avoid refeeding syndrome in cases of malnutrition
27
Q

What are the compartments used in Magnesium?

A
  • About 49.5% in cells
  • About 49.5% in bones
  • 1% in extracellular space
    • Intravascular space (Blood vessels, lymphatic vessels),
    • Interstitial space
      • 20% bound to proteins and 80% filtered to kidneys
28
Q

What are causes of Hypermagnaseamia?

A
  • Renal Failure
  • Increased ingestion of magnesium: Magnesium hydroxide, infusions
  • Tumour lysis syndrome
29
Q

What are some complications as a result of Hypermagnaseamia?

A
  • Delayed muscle contraction
    • Neuromuscular junction inhibition by inhibiting Ca2+ influx
  • Hypocalcaemia (inhibition of PTH hormone release)
    • Vasodilation
    • Muscle weakness
    • Diminished reflexes
    • Respiratory failure
    • Coma
  • Cardiac Arrhythmias (electrical potential altered)
    • Heart Block
    • Asystole
30
Q

What is the investigation and management of Hypermagnasaemia?

A

Blood tests for U&Es

Management

  • Reduce intake
  • Calcium gluconate
  • Furosemide to promote Mg2+ excretion
  • Dialysis in severe cases
31
Q

What are common causes of Hypomagnesaemia?

A
  • Renal Failure (less reabsorption)
  • Loop Diuretics (less positively charged lumen)
  • Genetic mutation in ion channels: Gitelman Syndrome
  • Prolonged Malnutrition
  • Low absorption in gut (PPI, Diarrhoea)
  • Uncontrolled diabetes mellitus
  • Hungry Bone syndrome (due to lack of thyroid hormone and PTH)
  • Alcoholism
32
Q

What are symptoms of Hypomagnasaemia?

A
  • Uncontrolled nerve stimulation
  • Tetany
  • Ataxia
  • Trousseau sign
  • Chvostek sign
  • Seizures
  • Convulsions
  • Abnormal Heart rhythms
33
Q

What are complications as result of Hypomagnasaemia?

A

Associated with :

  • Hypokalaemia
  • Hypocalcaemia
34
Q

What is the investigation and management of Hypomagnasaemia?

A

Blood tests for U&Es

Management

  • Oral supplementation
  • MgSO4 administered IV or IM

Year 3: Medicine Block ENDOCRINOLOGY (9 decks)

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