Calcium Part II Flashcards
List some symptoms of hypercalcaemia.
- Polyuria/polydipsia - due to osmotic diuresis
- Kidney stones
- Bone disease
- Constipation, pancreatitis
- Confusion, seizures, coma → NOTE: these tend to occur when calcium level >3 mmol/L
Bones, stones, abdominal groans, psychiatric moans
Difference in bone between osteoporosis and osteomalacia
osteoporosis - ratio of osteoid to bone is normal
osteomalacia - bone is decalcified
What are the main causes of primary hyperparathyroidism?
- Parathyroid adenoma
- Parathyroid hyperplasia (associated with MEN1) - all 4 glands are active
- Parathyroid carcinoma
Cause of high Ca2+ with low PTH
- Malignancy (most common)
- Others - sarcoid, thyroxicosis, vitamin D excess, milk alkali syndrome (antacids - alkalosis makes you absorb more Ca2+)
normal response to high Ca2+ is low PTH
Cause of high Ca2+ with normal/high PTH
How to differentiate between them
- Primary hyperparathyroidism - urine Ca2+ will be high
- Familial hypocalciuric hypercalcemia (rare) - cells have higher Ca2+ threshold, asymptomatic, urine Ca2+ will be low
normally PTH should be suppressed if Ca2+ is high
Outline the serum biochemistry features of primary hyperparathyroidism.
- High calcium
- Inappropriately raised PTH (could be within normal range but this is still inappropriate in hypercalcaemia)
- Low phosphate (phosphate trashing hormone)
Outline the pathophysiology of familial benign hypercalcaemia.
A mutation in the calcium-sensing receptor (CaSR) leads to a reduced threshold for PTH release (leads to mild hypercalcaemia)
Why don’t patients with familial benign hypercalcaemia get kidney stones?
PTH causes increased renal calcium absorption, thereby reducing urine calcium
Familial hypocalcuric hypercalcaemia
What are the three types of hypercalcaemia of malignancy?
- Humoral hypercalcaemia of malignancy (e.g. small cell lung cancer) → high calcium caused by PTHrP release
- Bone metastases (e.g. breast cancer) → high calcium caused by local bone osteolysis
- Haematological malignancy (e.g. myeloma) → high calcium caused by cytokines
NOTE: PTH will be low
List some other non-PTH driven causes of hypercalcaemia.
- Sarcoidosis (sarcoid tissue expresses 1 alpha hydroxylase)
- Thyrotoxicosis (increases bone resorption)
- Hypoadrenalism (reduced renal Ca2+ transport)
- Thiazide diuretics (reduced renal Ca2+ transport)
- Excess vitamin D (e.g. sun beds, excess active synthetic vitamin D)
thyroxine increases cell turnover in tissues
Loop diuretics increase urinary Ca2+
Outline the management of hypercalcaemia.
- Fluids, fluid and more fluids! (0.9% normal saline, 1L every 1 hour for 3-4hrs)
- Bisphosphonates but only if there is cancer (stops cancer from eating bone)
- Treat the underlying cause.
Furosemide to increase urinary Ca2+
List some symptoms and signs of hypocalcaemia
- Neuromuscular excitability (Chvostek’s sign - twitch when tap facial nerve, Trousseau’s sign - carpopedal spasm with BP cuff)
- Stridor (due to laryngeal spasm)
- Prolongs QT - more concerned about neuro issue
Need to give Ca2+ treat before causes seizure
Recall some differentials for hypocalcaemia when the PTH is high
This is an appropriate response to low calcium - SECONDARY HYPERPARATHYROIDISM
Could be due to:
- Vit D deficiency (most common cause)
- CKD (as low renal alpha-1-hydroxylase)
- Pseudohypoparathyroidism (gene deficit –> PTH resistance)
Recall some differentials for hypocalcaemia when the PTH is low
This is an inappropriate response (low calcium should cause high PTH)
Could be due to:
- Surgical mishap during thyroidectomy
- Autoimmune hypoparathyroidism (rare)
- Di George syndrome (even rarer! Agenesis of parathyroids)
- Magnesium deficiency - need Mg2+ to make PTH, can be caused by OMEPRAZOLE
