Hypercalcaemia/Parathyroid Disease Flashcards
How much of plasma calcium is bound to albumin?
40% (inactive)
Non-bound is ionized
What effect do acidotic states have on ionized calcium level?
Increase ionized calcium level by decreasing protein binding
What effect do alkalotic states have on ionized calcium level?
Decrease ionized calcium level by increasing protein binding
What are the main factors controlling plasma calcium level?
PTH
Vit D
Calcitonin
Where is PTH produced?
Chief cells in parathyroid glands
When is PTH secreted?
Low plasma calcium
Low Vit D
High phosphate
What are the effects of PTH?
Raises plasma calcium
-stimulates cal reabsorption from bone
-increases renal tubular cal reabsorption
-stimulates increased GI cal absorption (indirect)
Increases renal phosphate excretion
Where is Vitamin D produced?
Synthesised in skin (D3 cholecalciferol)
Ingested (D2 ergocalciferol) –> hydroxylated in liver to 25-OH-D2/3 –> hydroxylated in kidney to active Vit D
What are the effects of Vitamin D?
Increases absorption of calcium & phosphate from GI tract
Required for normal bone formation
What are the causes of Vitamin D deficiency?
Inadequate sunlight exposure (rickets)
Malabsorptive conditions
Liver/kidney disease
Where is Calcitonin produced?
Parafollicular C cells of thyroid gland
When is Calcitonin secreted?
Increased plasma calcium
What are the effects of Calcitonin?
Decreases plasma calcium by antagonising the effect of PTH on bone
What determines intestinal uptake of calcium?
Ionized calcium levels in lumen
Presence of activated Vit D
What determines renal excretion of calcium?
Na reabsorption in proximal tubule (90%)
PTH regulation in distal tubule (10%)
What is hypercalcaemia?
Plasma calcium >2.5mmol/L
What is the most common cause of hypercalcaemia?
1o hyperparathyroidism/malignancy (97%)
What are the causes of excessive PTH secretion, leading to hypercalcaemia?
1o hyperparathyroidism
3o hyperparathyroidism
Ectopic PTH secretion (v. rare)
What are the malignant causes of hypercalcaemia?
Myeloma
Metastatic deposits in bone
Paraneoplastic (SCC)
What are the causes of excess Vit D, leading to hypercalcaemia?
Exogenous excess
Granulomatous disease (TB, sarcoid)
Lymphoma
What are the causes of excess calcium, leading to hypercalcaemia?
Milk-alkali syndrome
-antacids increase absorption of calcium
What are the other endocrine causes of hypercalcaemia?
Thyrotoxicosis
Addison’s
What are the renal causes of hypercalcaemia?
Severe AKI
What are the iatrogenic causes of hypercalcaemia?
Thiazide diuretics
Lithium
What are the hereditary causes of hypercalcaemia?
Familial hypocalciuric hypercalcaemia
What is the cause of 1o hyperparathyroidism?
Single parathyroid adenomas (80%)
Diffuse glandular hyperplasia (20%) - MEN IIa/IIb
How can PTH levels distinguish b/w hyperparathyroidism & malignancy?
High in hyperparathyroidism
Low in malignancy
What are the PTH/calcium levels like in 1o hyperparathyroidism?
PTH high
Calcium high
How is 1o hyperparathyroidism managed?
Parathyroidectomy
What is the major complication of parathyroidectomy?
Post-op hypocalcaemia
Give adcal for 14/7
What is 2o hyperparathyroidism?
Physiological hypertrophy of all parathyroid glands, in response to hypocalcaemia
In which pts is 2o hyperparathyroidism seen?
Renal disease
Vit D deficiency
What are the PTH/calcium levels like in 2o hyperparathyroidism?
PTH high
Calcium low/normal
What is the cause of 3o hyperparathyroidism?
Long-standing 2o hyperparathyroidism
Occurs mostly in renal failure
What are the PTH/calcium levels like in 3o hyperparathyroidism?
PTH high
Calcium high
Phosphate grossly high
What is the management of 2o hyperparathyroidism?
Address cause of hypocalcaemia
What is the management of 3o hyperparathyroidism?
Parathyroidectomy
How does 1o hyperparathyroidism present?
Often asymptomatic
Sx related to hypercalcaemia
What are the sx of hypercalcaemia?
Bones - bone pain, fractures, muscle weakness
Stones - renal stones, polyuria, AKI/CKD
Groans - abdo pain, vom, const, pancreatitis, GI ulcers
Moans - depression, confusion, tiredness, hypotonicity
What investigations are appropriate in suspected 1o hyperparathyroidism?
PTH (raised) Ca (raised) PO4 (low) ALP (raised) 24hr urinary calcium (raised) DXA scan (assess osteoporosis) Technetium/USS (localise tumour)
How can 1o hyperparathyroidism be distinguished from familial hypocalciuric hypercalcaemia?
In FHH low 24hr urinary calcium
Can use spot calcium:creatinine excretion
How can 1o hyperparathyroidism be distinguished from 3o hyperparathyroidism?
Clinical presentation PO4 levels (low/normal in 1o)
What syndromes is 1o hyperparathyroidism associated with?
Multiple Endocrine Neoplasia
-autosomal dominant
What tumours does MEN I produce?
Parathyroid hyperplasia/adenoma
Pancreatic endocrine tumours (gastrinoma/insulinoma)
Pituitary adenoma
What tumours does MEN IIa produce?
Thyroid medullary carcinoma
Adrenal PCC
Parathyroid hyperplasia
What tumours does MEN IIb produce?
MEN IIa
Mucosal neuromas
Marfanoid appearance
No hyper PTH
What is the immediate management of a patient presenting w/ acute hypercalcaemia?
If Ca >3.5mmol/L AND sev sx
- IV fluids (0.9% NaCl, 3-6L/24hrs, diuretics if overloaded)
- Bisphosphonates (pamidronate, lowers Ca over 2-3/7)
- Calcitonin (rapidly reduce Ca, short-lived)
- Dialysis (if renal impairment)
What is the non-immediate management of a patient presenting w/ acute hypercalcaemia?
Investigate/treat cause of hypercalcaemia
When are steroids used in hypercalcaemia?
If hypercalcaemia due to myeloma, lymphoma or sarcoid
What is the potentially life threatening complication of 1o hyperparathyroidism?
Reduced QT interval
Can lead to cardiac arrest
