Calcium Disturbance

Question 1

Normal range of Calicum

Answer 1

2.2-2.6

Question 2

What are the causes of hypercalcaemia

Answer 2

PTH suppressed
- Malignancy
- Sarcoidosis
- vit D excess
- Thyrotoxicosis
- Thiazide diuretics
- Hypoadrenalism
- milk alkali syndrome (excess of Rennie sweet consumption)

PTH not suppressed
- Primary hyperparathyroidism (most common community cause of hyperCa)
- Familial hypocalciuric hypercalcaemia

Question 3

What are the causes of primary hyperparathyroidism

Answer 3

Parathyroid adenoma (80%)
Parathyroid hyperplasia
Parathyroid carcinoma (0/%)
MEN1 (adenoma) MEN2 (hyperplasia)

Question 4

Why might people with sarcoidosis get hypercalcaemia

Answer 4

1-alpha hydroxylase can be expressed unregulated in lung cells of sarcoid tissue → increases renal and intestinal abs. of Ca

Question 5

What are the symptoms of hypercalcaemia

Answer 5

Polyuria/polydipsia (osmotic diuretic effect) + dehydration
Constipation (slows nerves/muscles)

Calcium >3.0mmol/L: Neuro - confusion/seizures/coma

Question 6

Describe familial benign/hypocalciuric hypercalcaemia (FBH/FHH)

Answer 6

Mutation in CaSR which usually detects the level of Ca for the parathyroid gland
This increases the set point for PTH release → mild hypercalcaemia
Benign condition - do not form kidney stones + reduced urine calcium

Gland removal will not cure it - surgery not required

Question 7

What are the causes of Hypercalcaemia of malignancy

Answer 7

1. Humoral e.g. sq lung cancer releasing PTHrp → dissolves bone
2. Bone mets e.g. breast cancer causing local bone osteolysis (most common)
3. Haem. malignancy e.g. myeloma

Question 9

How is hypercalcaemia managed

Answer 9

1. Fluid resus (pt will be dehydrated)
   - 0.9% saline 1L over the first 1-2 h
   - re-measure → 4-6L over 24h
2. Bisphosphonates if the cause is known to be cancer
3. Treat underlying cause e.g. surgery

Question 10

How are causes of hypercalcaemia differentiated on investigation

Answer 10

Albumin raised → unlikely to be true hyperCa
Urea raised = dehydration
Urea normal = cuffed specimen

Albumin normal/low:
Phosphate low → primary or tertiary hyperparathyroidism

Phosphate high:
ALP raised: bone mets, thyrotoxicosis, sarcoidosis
ALP normal: myeloma, excess vit D, sarcoidosis, milk alkali syndrome

Question 11

What are the causes of hypocalcaemia

Answer 11

PTH driven (low PTH)
Surgical e.g. post thyroidectomy
Auto-immune hypoparathyroidism
Congenital absence of parathyroids e.g. DiGeorge syndrome
Mg deficiency (PTH regulation)

non-PTH driven
vitamin D deficiency - dietary, malabsorption, lack of sunlight
CKD (1a-hydroxylase not produced → reduced Ca resorption → hypoCa → PTH stimulated → secondary hyperPTH → hyperCa → tertiary hyperPTH )
PTH resistance (pseudohypoparathyroidism)

Question 12

What are the clinical features of hypocalcaemia

Answer 12

Neuro-muscular excitability
- Chvosteks sign (fascial nerve excitability, twitching of facial muscles in response to tapping over the facial nerve – 29% sensitive)
- Trousseaus sign (carpopedal spasm induced by pressure - latent tetany – 94% sensitive)
- Hyperreflexia
- Convulsions
- Laryngeal spasm → stridor
- Choked optic disk
- Prolonged QT
- Peri-oral paraesthesia

Question 13

What is the management for hypocalcaemia

Answer 13

symptomatic, Ca <1.875 → 10% Calcium gluconate IV
Asymptomatic, mild → oral supplementation e.g. SandoCal
Low vit D → vit D supplementation with alfacalcidol (CKD) or vit D2/D3