Endocrinology - Hypocalcaemia

Question 1

suggest possible causes for hypocalcaemia

Answer 1

1. Hypoparathyroidism (low PTH levels): parathyroid agenesis, parathyroid destruction (e.g. surgery, sarcoidosis), autoimmune
2. 2ndary hyperparathyroidism (high PTH levels): vitD deficiency (CKD, malnutrition, malabsorption, liver disease…), pseudohypoparathyroidism (PTH resistance), hypomagnesaemia
3. Drugs: calcium chelators (e.g. citrate in blood transfusions), bone resorption inhibitors (bisphosphonates, calcitonin), phenytoin (affects vitD)
4. Acute pancreatitis, acute rhabdomyolysis, toxic shock syndrome
5. Malignancy: tumour lysis or osteoblastic metastases (e.g. prostate cancer)

Question 2

describe the possible presentation of hypocalcaemia

Answer 2

Caused by decreased threshold for AP generation:

• paraesthesia (usually fingers, toes and around mouth)
• muscle cramps
• seizures or tetany
• carpopedal spasm
• laryngospasm or bronchospasm
• prolonged QT interval, which may progress to ventricular fibrillation or heart block

Question 3

describe 2 signs that can be elicited in hypocalcaemia

Answer 3

1. Chvostek’s sign (feature of latent tetany): tapping over course of facial n. provoked spasm of face, mouth or nose
2. Trousseau’s sign (due to enhanced neuromuscular excitability): inflating cuff to pressure above pt’s systolic level and maintain for several mins causing carpopedal spasm

Question 4

which Ix should you perform on a pt with suspected hypocalcaemia

Answer 4

1) Bloods:
- UandEs, inc. calcium, corrected calcium, magnesium and phosphate - diagnostic, check for CKD
- serum albumin - to measure corrected calcium value
- PTH, ALP, vitD - help determine cause
- amylase - exclude acute pancreatitis
- creatine kinase - exclude rhabdomyolysis

2) ECG: exclude dysrhythmias and prolonged QT interval

Question 5

A pt with hypocalcaemia has a blood test which also shows:

• raised PTH
• raised serum phosphate
• raised ALP
• raised creatinine

What is the likely cause?

Answer 5

CKD

Question 6

A pt with hypocalcaemia has a blood test which also shows:

• low/undectable PTH
• raised serum phosphate
• normal ALP
• normal vitD metabolites

What is the likely cause?

Answer 6

hypoparathyroidism

Question 7

A pt with hypocalcaemia has a blood test which also shows:

• raised PTH
• raised serum phosphate
• normal ALP
• normal creatinine

What is the likely cause?

Answer 7

pseudohypoparathyroidism

Question 8

A pt with hypocalcaemia has a blood test which also shows:

• raised PTH
• decreased serum phosphate
• raised ALP
• decreased vitD metabolites (e.g. 25(OH)D3)

What is the likely cause?

Answer 8

vitD deficiency or malabsorption

Question 9

how would you manage a symptomatic hypocalcaemia pt (seizures, tetany)?

Answer 9

1. 10 ml (2.25 mmol) CALCIUM GLUCONATE 10% by slow IV injection - repeat as necessary or follow with infusion
2. +/- oral calcium preparations as supplement or if IV access difficult
3. monitor serum calcium regulalry
4. if hypomagnesaemic, correct magnesium level

Question 10

how would you manage persistent hypocalcaemia in long-term?

Answer 10

1. supplementary calcium initially (can be discontinused once stabilised)
2. calcitriol, vitD2 or D3