Calcium homeostasis and disorders of calcium metabolism Flashcards
Describe what happens when calcium levels drop
Parathyroid gland secreted PTH
=kidneys to reabsorb calcium and excrete phosphate
=bone resorption to get calcium and phosphate
=gut absorption of calcium and phosphate
Activated vit D is needed for calcium absorption in the gut
Describe how vit D is synthesised and activated?
UV light converts pre-vit D to vit D
Vit D has to go first through liver (liver enzyme) and then through kidney (kidney enzyme) to be activated
What are the acute and chronic symptoms of hypercalcaemia?
Acute: thirst, dehydration, confusion, polyuria
Chronic: myopathy, osteopaenia, fractures, depression, hypertension,
abdominal pain- pancreatitis, ulcers, renal stones
“Stones, groans, bones, psychic moans “
What are the causes of hypercalcaemia?
Common:
¥ Primary Hyperparathyroidism
¥ Malignancy
Others: ¥ Drugs: vit D, thiazides ¥ Granulomatous Disease eg Sarcoid, TB ¥ Familial Hypocalciuric hypercalcaemia ¥ High turnover: bedridden, thyrotoxic, Pagets ¥ Others ¥ Tertiary hyperparathyroidism
What is the diagnosis of secondary hyperparathyroidism?
¥ Raised serum calcium
¥ Raised serum PTH (or inappropriately normal)
¥ Increased urine calcium excretion
How does malignancy cause hypercalcaemia and how is this diagnosed?
Mechanisms:
¥ Metastatic Bone destruction
¥ PTHrp from solid tumours
¥ Osteoclast activating factors
Diagnosis:
Raised calcium and alkaline phosphatase
X-ray, CT, MRI
Isotope Bone Scan
What is the acute treatment of hypercalcaemia?
¬ Fluids- rehydrate with 0.9% saline 4-6L in 24hours
¬ Consider loop diuretics once rehydrated- avoid thiazides
¬ Bisphosphonates- single dose will lower Ca over 2-3d, maximum effect at 1 week
¬ Steroids occasionally used e.g Pred 40-60mg/day for sarcoidosis
¬ Salmon calcitonin- rarely used
¬ Chemotherapy may reduce calcium in malignant disease e.g. myeloma
Hypocalcuric hypercalcaemia - what is this?
- what are the causes?
- what is the diagnosis?
low levels calcium in urine and high levels calcium in blood
Causes:
♣Familial (Aut Dom) Deactivating mutation in the calcium sensing receptor
♣Usually Benign/ assymptomatic
Diagnosis: Mild Hypercalaemia Reduced urine calcium excretion PTH may be (marginally) elevated Genetic Screening
Hypocalcaemia:
what are the signs and symptoms?
¥ Paraesthesia - fingers, toes, perioral ¥ Muscle cramps, tetany ¥ Muscle weakness ¥ Fatigue ¥ Bronchospasm or laryngospasm ¥ Fits ¥ Chovsteks sign (tapping over facial nerve) ¥ Trousseau sign (carpopedal spasm) ECG: QT prolongation
What are the causes of hypocalcaemia?
¬ Hypoparathyroidism
¬ Vitamin D deficiency (osteomalacia/rickets)
¬ Chronic renal failure
Others: pancreatitits/hyperventilation/osteoblastic bone metastases/rhabdomyolysis
What is the treatment of acute hypocalcaemia?
IV Calcium Gluconate – 10ml, 10% over 10mins (in 50% saline or dextrose)
Infusion:
10ml 10% in 100ml infusate at 50ml/hr
What are the causes of rickets and osteomalacia?
¥ Dietary deficiency ¥ Malabsorption: gastric surgery, coeliac disease, liver disease, pancreatic failure ¥ Chronic renal failure ¥ Lack of sunlight ¥ Drugs eg anticonvulsants
What is seen clinically in rickets and osteomalacia?
¥ Low calcium
¥ Muscle wasting - proximal myopathy
¥ Dental Defects (caries, enamel)
¥ Bone. Tenderness, fractures, rib deformity, limb deformity
how does chronic renal disease cause secondary hyperparathyroidism?
chronic hypocalcaemia due to vit D deficiency
-titrate treatment to PTH levels
What are the long term consequences of vit D deficiency?
¬ Demineralisation/ Fractures
¬ Osteomalacia/ Rickets
Malignancy (especially colon), Heart Disease, diabetes etc
