Hypo - And Hypercalcaemia Flashcards
What is role of calcium
- Average person has 1kg of calcium. 99% in skeleton
- Ionised calcium in ECF (<1%)
- Cofactor in coagulation
- Skeletal mineralisation
- Membrane stabilisation (Neuronal conduction)
- ideal serum levels 1.1mmol/l
Describe the calcium homeostasis existing between the intestine bone and kidney
• 1000mg goes into the intestine every day
- 400mg is absorbed
- 200mg is reabsorbed back into the intestine
- 800mg secreted
- 500mg goes into the adult bone every day
- 10000mg excreted into the kidney
- 9800mg reabsorbed back
Describe calcium homeostasis in response to a decrease in serum calcium
• When calcium levels go low - PTH is released
Describe the actions of Parathyroid Hormone (PTH)
KIDNEYS:
- increased calcium reabsorption
- decreased phosphate reabsorption
- increases hydroxylation of 25-OH it D
BONE:
- Increased bone remodelling
- Bone respiration exceeds bone formation
GUT:
No direct effect
Ca absorption increases due to increased 1,25(OH)2 vitD
What should be considered when measuring for hypocalcaemia
• Low serum albumin
Is it always inappropriate when there are abnormalities in levels of PTH
No there may be cases where the body releases excess PTH to compensate for the low calcium serum levels
e.g.) Vit D deficiency leads to low calcium levels
Why might a test in low calcium not necessarily mean hypocalcaemia
“Corrected calcium” should only be recorded.
• Low serum albumin results in low ‘total serum calcium’ BUT NOT low ionised calcium.
• Corrected calcium = total serum calcium + 0.02
What causes Hypocalcaemia
- Vitamin D deficiency/Osteomalacia
- Hypoparathyroidism:
- Post surgery, radiation, autoimmune disease
- Hereditary
- Infiltration (Wilson’s disease)
- Chronic renal failure
- Magnesium deficiency
- Pseudohypoparathyroidism
- Acute pancreatitis
Consequences of Hypocalcaemia
• Parasthesia
• Muscle spasm
- hands and feet
- Seizures
- Basal ganglia calcification
- Cataracts
- Dental hypoplasia
- ECG abnormalities (Long QT interval)
How can we test for hypocalcaemia?
- Tap over facial nerve - look for spasm of facial muscles (Chvostek’s sign)
- Inflate blood pressure cuff to 20mmHG above systolic for 5 mins - should see flexion of hand (Italian hand) - Trousseau’s sign
What clues can we look for to diagnose hypocalcaemia
- Neck surgery history
- Family history to suggest genetic cause
- Drug history (e.g. anti epileptics)
- Growth failure, hearing loss
- Neck scar, candidiasis
Describe how decreased PTH leads to overall decreased serum calcium
• Decreased renal calcium reabsorption (increased calcium excretion)
• Increased renal phosphate reabsorption
(increased serum phosphate)
- Decreased bone resorption
- Decreased formation of 1,25(OH) vitD (decreased intestinal calcium absorption)
How can we manage Hypocalcaemia
MILD: ( > 1.9mmol/L)
- oral supplements
- If vitD deficient, cholecalciferol for 12 weeks
- If hypomagnesaemia, replace magnesium
SEVERE: ( < 1.9mmol/L)
- 10-20mls of 10% calcium gluconate over 10 mins
- Dilute 100mls of 10% calcium gluconate in 1L of normal saline
- Post op hypocalcaemia/hypoparathyroidism a(thyroidectomy) give 1-alphacalcidol 0.25mcg/day
What are the causes of hypercalcaemia
• MALIGNANCY
- bone mets, myeloma, PTHrP, lymphoma
- PRIMARY HYPERPARATHYROIDISM
- Thiazides
- Sarcoidosis
- Immobilisation
- Milk-alkali syndrome (taking antacids)
- Adrenal insufficiency
- Phaeochromocytoma
Symptoms and Consequences of Hypercalcaemia
SYMPTOMS • Thirst, polyuria • Nausea • Constipation • Confusion coma
CONSEQUENCES • Pancreatitis • Gastric ulcer • Renal stones • ECG abnormalities (Short QT)
