Clinical calcium homeostasis Flashcards
The title says it all really
What are the causes of hypocalcaemia?
- Disruption to the thyroid gland following total thyroidectomy (may be temporary or permanent)
- Following selective thyroidectomy (usually transient and mild)
- Severe vitamin D deficiency (common)
- Magnesium deficiency (proton pump inhibitors e.g. omeprazole can causes this)
- Cytotoxic drug-induced hypocalcaemia
- Pancreatitis, rhabdomyolysis and large volume blood transfusion
When does sympptoms of hypocalcaemia start to develop?
when serum calcium falls below 1.9mmol/L (this threshold does vary and is dependent of the rate of fall)
What are the symptoms of acute hypocalcaemia?
□ Neuromuscular irritability (tetany)
® Paraesthesia
® Muscle twitching
® Carpopedal spasm
® Trousseau's sign
® Chvostek's sign
® Seizures
® Laryngospasm
® Bronchospasm
□ Cardiac
® Prolonged QT interval
® Hypotension
® Heart failure
® Arrhythmia
® PapilledemaWhat are the chronic signs and symptoms of hypocalcaemia?
□ Ectopic calcification (basal ganglia) □ Extrapyramidal signs □ Parkinsonism □ Dementia □ Subcapsular cataracts □ Abnormal dentition □ Dry skin
What are the investigations for hypocalcaemia?
○ ECG ○ Serum calcium ○ Albumin ○ Phosphate ○ PTH ○ U&Es ○ Vitamin D ○ Magnesium
What will the results be if someone has hypoalbuminemia?
- Low total calcium
- Normal ionised calcium
- Normal phosphate
- Normal PTH
What will the results be if someone has alkalosis?
- Normal total calcium
- Low ionised calcium
- Normal phosphate
- Normal/ high PTH
What will the results be if someone has vitamin D deficiency?
- Low total calcium
- Low ionised calcium
- Low phosphate
- High PTH
What will the results be if someone has chronic renal failure?
- Low total calcium
- Low ionised calcium
- High phosphate
- High PTH
What will the results be if someone has hypoparathyroidism?
- Low total calcium
- Low ionised calcium
- High phosphate
- Low PTH
What will the results be if someone has pseudohypoparathyroidism?
- Low total calcium
- Low ionised calcium
- High phosphate
- High PTH
What will the results be if someone has acute pancreatitis?
- Low total calcium
- Low ionised calcium
- Low/ normal phosphate
- High PTH
What will the results be if someone has hypomagnesaemia?
- Low total calcium
- Low ionised calcium
- Variable phosphate
- Low or normal PTH
What is the treatment of mild hypocalcaemia? (also what counts as mild?)
(asymptomatic, >1.9mmol/L)
- Commence oral calcium tablets
- If post thyroidectomy repeat calcium 24 hours later
- If vitamin D deficient, start vitamin D
- If low Mg2+, stop any precipitating drug and replace Mg2+
What is the treatment of severe hypocalcaemia?
(symptomatic or <1.9mmol/L)
- This is a medical emergency
- Administer IV calcium gluconate
- Initial bolus (10-20 ml 10% calcium gluconate in 50-100ml of 5% dextrose IV over 10 minutes with ECG monitoring)
- Calcium gluconate infusion
- Treat the underlying cause
What are the parathyroid mediated causes of hypercalcaemia?
□ Primary hyperparathyroidism (sporadic)
□ Inherited variants
® Multiple endocrine neoplasia (MEN) syndromes
® Familial isolated hyperparathyroidism
® Hyperparathyroidism- jaw tumour syndrome
□ Familial hypocalciuric hypercalcemia
□ Tertiary hyperparathyroidism (renal failure)
What are the non-parathyroid mediated causes of hypercalcaemia?
□ Hypercalcaemia of malignancy
® PTHrp
® Activation of extrarenal 1 alpha-hydroxylase (increased calcitriol)
® Osteolytic bone metastases and local cytokines
□ Vitamin D intoxication
□ Chronic granulomatous disorders
® Sarcoid, TB, Berylliosis, Histoplasmosis, Wegener’s
What medications cause hypercalcaemia?
□ Thiazide diuretics □ Lithium □ Teriparatide □ Excessive vitamin A □ Theophylline toxicity
What are the miscellaneous causes of hypercalcaemia?
□ Hyperthyroidism □ Acromegaly □ Pheochromocytoma □ Adrenal insufficiency □ Immobilisation □ Parenteral nutrition □ Milk alkali syndrome
What are the main clinical features of hypercalcemia?
- Renal: Polyuria, Polydipsia, Kidney stones
- GI: Anorexia, constipation, nausea and vomiting
- MSK: Muscle weakness
- Neuro: decreased concentration
- Cardiovascular: shortening of the QT intervals
What investigations are done for hypercalcemia?
- U&Es
- Ca
- PO4
- Alk phos
- Myeloma screen
- Serum ACE
- PTH
- Consider ECG
What is the treatment of hypercalcaemia?
- Rehydration
□ 0.9% Saline 4-6 litres over 24 hours
□ Monitor for fluid overload
□ Consider dialysis if severe renal failure - After rehydration, intravenous bisphosphonates
□ Zoledronic acid 4mg over 15 mins
□ Give more slowly and consider dose reduction if renal impairment
□ Calcium will reach nadir at 2-4 days
Explain primary hyperparathyroidism
- Most patients are asymptomatic at diagnosis
- Most cases are sporadic but has been associated with neck irradiation or prolonged lithium use
- 85% parathyroid adenoma
- 15% four gland hyperplasia
- <1% MEN type 1 or 2A
- <1% parathyroid carcinoma
- Often present for years prior to diagnosis
What are the investigations for hyperparathyroidism?
○ Ca, PTH ○ U&Es: check renal function ○ Abdominal imaging: renal calculi ○ DEXA: osteoporosis ○ 24 hour urine collection for calcium: Excl. FHH ○ Vitamin D ○ Parathyroid ultrasound ○ SESTAMIBI
