Hyper/hypocalcaemia Flashcards
What is normal range for calcium?
2.2-2.6 mmol/L
What are causes of hypocalcaemia with increased PO43-?
- CKD
- Hypoparathyroidism
- Pseudohypoparathyroidism
- Acute rhabdomyolysis
- Hypomagnasemia
What are causes of hypocalcaemia with high PTH (secondary hyperparathyroidism)?
Secondary hyperparathyroidism in response to hypocalcaemia
- Vit D deficiency
- Pseudohypoparathyroidism
- Hypomagnasemia
- Renal disease
- Tumour lysis syndrome
- Acute pancreatitis
- Acute respiratory alkalosis
What are causes of hypocalcaemia with low PTH?
Parathyroid dysfunction (primary/secondary)
- Destruction of parathyroid glands - Surgery, autoimmune, radiation, infiltration (iron, copper, tumour)
- Developmental parathyroid disorders - Isolated hypoparathyroidism, Autosomal recessive, autosomal dominant, or X-linked, Syndromes of hypoparathyroidism associated with complex developmental anomalies (e.g., DiGeorge sequence
- Hungry bone disease following parathyroidectomy.
- HIV infection
What is primary hypoparathyroidism?
Dysfunction of parathyroid gland - results in low PTH and low Ca2+ - hypocalcaemia
What are causes of primary hypoparathyroidism?
- Autoimmune hypoparathyroidism
- Congenital hypoparathyroidism
Why can hyperphosphataemia occur in primary hypoparathyroidism?
Hyperphosphataemia results from the lack of PTH action on renal phosphate transport to clear phosphate via the kidney - leads to phosphate accumulation
What are causes of secondary hypoparathyroidism?
- Radiation
- Surgery - thyroidectomy, parathyroidectomy
- Hypomagnesaemia
What is secondary hypoparathyroidism?
In secondary hypoparathyroidism, parathyroid gland dysfunction is the consequence of a primary problem elsewhere, typically sepsis or hypomagnesemia.
What are causes of hypocalcaemia with normal or decreased PO43-?
- Vitamin D deficiency
- Osteomalacia (increased ALP)
- Acute pancreatitis
- Overhydration
- Respiratory alkalosis
What are features of hypocalcaemia?
- Spasms - carpopedal spasm
- Perioral paraesthesiae
- Anxious, irritable, irrational
- Seizures
- Muscle tone increase in smooth muscle
- Orientation impaired + confusion
- Dermatitis
- Impetigo herpatiformis
- Chvostek’s signs, cataracts, chroeoathetosis, cardiomyopathy
What is Chvotsek’s sign?
Tapping on the patient’s cheek at a point anterior to the ear and just below the zygomatic bone to stimulate the facial nerve results in twitching of the ipsilateral facial muscles. It is suggestive of latent tetany and increased neuromuscular excitability
What is thought to be the mechnism of Chovtsek’s Sign in hypocalcaemia?
Increased neuronal excitability
Calcium is needed to maintain normal neuronal membrane permeability by acting on and blocking sodium channels on the neuronal membrane. If extracellular calcium is low and/or not available, the sodium channels are more permeable. As more sodium enters the cell, the cell becomes less polarised and is more easily stimulated to reach action potential
What is trousseau’s sign?
After inflating a cuff above the patient’s systolic blood pressure and leaving it inflated for 3 minutes, muscular contraction – including flexion of the wrist and MCP joints, hyperextension of the fingers and flexion of the thumb on the palm – occurs
How does respiratory alkalosis cause Chovstek’s Sign?
Respiratory alkalosis and hyperventilation result in less active ionised calcium – as opposed to total calcium. It is the decrease in ionised calcium that causes increased excitability
When the pH is high (alkalotic), more calcium binds to proteins, making less active calcium available in the extracellular fluid for regular processes, such as blocking sodium channels and maintaining membrane stability
What is thought to be the mechanism behind Trousseau’s sign?
Similar mechanism to Chvostek’s sign
In hypocalcaemia, what are symptoms of increased smooth muscle tone in hypocalcemia?
- Colic
- Wheeze
- Dysphagia
What cardiac problems can manifest in hypocalcaemia?
- Prolonged QT
- Hypotension
- HF
- Arrythmias
What are features of chronic hypocalcaemia?
- Ectopic Calcification (basal ganglia)
- Extrapyramidal signs
- Parkinsonism
- Dementia
- Subcapular cataracts
- Abnormal dentition
- Dry Skin
If someone had hypocalcaemia, what test would you want to look at?
PTH
If someone had hypocalcaemia with low/normal PTH, what would you check?
Magnesium
If someone had hypocalcaemia, with low PTH, and low magnesium, what might be the cause of hypocalcaemia?
Magnesium defciiency
What might hypocalcaemia with low/normal PTH and normal magnesium suggest as the cause of hypocalcaemia?
Hypoparathyroidism or calcium sensing receptor defect
What might you do if you investigated PTH in someone with hypocalcaemia and the PTH was high?
Check U+E’s
What might hypocalcaemia with high PTH and high urea and creatinine suggest as the cause of hypocalcaemia?
Renal failure
What investigation might you do in someone with hypocalcaemia with high PTH and normal U+E’s?
Check vitamin D
What might cause hypocalcaemia with high PTH, normal U+E’s, and low vitamin D?
Vitamin D deficiency
What might cause hypocalcaemia with increased PTH with normal U+E’s and normal Vitamin D?
Pseudohypoparathyroidism or calcium deficiency
What might you see on investigation of the following in someone with hypocalcaemia caused by Vitamin D deficiency:
- Total calcium
- Ionised calcium
- Phosphate
- PTH
- Total calcium - low
- Ionised calcium - low
- Phosphate - low
- PTH - High
What might you see on investigation of the following in someone with hypocalcaemia caused by Hypoparathyroidism:
- Total calcium
- Ionised calcium
- Phosphate
- PTH
- Total calcium - low
- Ionised calcium - low
- Phosphate - High
- PTH - low
What might you see on investigation of the following in someone with hypocalcaemia caused by CKD:
- Total calcium
- Ionised calcium
- Phosphate
- PTH
- Total calcium - low
- Ionised calcium - low
- Phosphate - High
- PTH - High
What might you see on investigation of the following in someone with hypocalcaemia caused by Respiratory alkalosis:
- Total calcium
- Ionised calcium
- Phosphate
- PTH
- Total calcium - normal
- Ionised calcium - low
- Phosphate - normal
- PTH - normal/high
What investigations would you consider doing in someone with hypocalcaemia?
- Bedside - ECG, Urinalysis
- Bloods - Serum total calcium, serum albumin, phosphate, PTH, U+E’s, Vit D, Magnesium, Amylase, CK
- Imaging - Consider X-ray
What might you see on investigation of the following in someone with hypocalcaemia caused by Respiratory alkalosis:
- Total calcium
- Ionised calcium
- Phosphate
- PTH
- Total calcium - normal
- Ionised calcium - low
- Phosphate - normal
- PTH - normal/high
What might you see on investigation of the following in someone with hypocalcaemia caused by Acute pancreatitis:
- Total calcium
- Ionised calcium
- Phosphate
- PTH
- Total calcium - low
- Ionised calcium - low
- Phosphate - normal/low
- PTH - high