Clinical Calcium Homeostasis Flashcards
Functions of Calcium?
Bone formation Cell division and growth Muscle contraction Neurotransmitter release
What proportion of Ca is bound in plasma and to what?
45% bound mainly to albumin
10% in non-ionised or complexed to other molecules
45% is ionised - biologically important
Normal range of Ca in clinical practice?
2.20-2.60 mmol/l
How do we calculate free calcium?
Increased albumin decreases free calcium and vice versa
Adjust Ca2+ by 0.1mmol/l for each 5g/l reduction in albumin from 40g/l
Mr Bloggs has a Calcium of 2.55mmol/L, his
albumin is 30g/L. What is his corrected calcium?
2.75mmol/L
What does acidosis do to calcium?
Increases levels of free Ca2+ predisposing to hypercalcaemia
What do chief cells in parathyroid glands respond to?
Directly to changes in calcium conc.
Alterations in ECF calcium levels are transmitted into the parathyroid cells via…
Calcium sensing receptor (CaSR)
PTH is secreted in response to..?
A fall in calcium
What does PTH do?
Promotes reabsorption of Ca from renal tubules and bone
Mediates conversion of Inactive Vit. D to active
What levels of calcium indicate hypocalcemia?
<2.20 mmol/l
What 2 categories of symptoms does acute hypocalcemia cause?
Neuromuscular
Cardiac
Name some neuromuscular symptoms of acute hypocalcaemia.
Paresthesia Muscle twitching Carpopedal spasm Trousseau's and Chovstek's sign Seizures Broncho and Laryngo spasms
What is Trousseau’s sign?
BP cuff inflated to 20mmHg above systolic bp, blood cut off for 5 mins
Hand goes into like an Italian hand
What is Chovstek’s sign?
Tap facial nerve and lip will twitch or facial muscles will spasm (depending on severity of hypocalcaemia)
What is the cardiac symptoms of acute hypocalcaemia?
Prolonged QT interval Hypotension Heart failure Arrythmia Papilloedema
Symptoms of chronic hypocalcaemia?
Ectopic calcification Extrapyramidial signs Parkinsonism Dementia Dry skin
Causes of hypocalcaemia with a low PTH (1y)?
Thyroid surgery Genetic Autoimmune Infiltration Radiation induced destruction of PT gland
Causes of hypocalcaemia with a high PTH (2y)?
Vit. D deficiency
Pseudohypoparathyroidism
Magnesium deficiency
Renal disease
Acute pancreatitis
Acute respiratory alkalosis
Diagnostic approach for hypocalcaemia?
Hx - ask about vitamin intake and meds, previous surgeries, FHx and autoimmune risks
Examination - look for scars or surgery
Investigations - ECG, serum Ca2+, albumin, Vit D, Magnesium, PTH
Also phosphate, U&Es
Why would we check PTH?
See if its a 1y or 2y cause
If PTH shows as high - 2y cause - what would you check next? Why?
Urea and Creatine - if low it is renal failure
U&Es are normal, what else can we check?
Vitamin D levels if its a deficiency
If PTH was low or normal - indicating a 1y cause - what would we check for and why?
Magnesium - if low its a deficiency
If normal it’s a problem with the glands - hypoparathyroidism OR a rare calcium sensing receptor defect
What is Pseudohypoparathyroidism, when does it present?
A group of disorders where PTH is not effective on its target organs - kidney and
bone
Results in hypocalcaemia, hyperphosphatemia and ELEVATED PTH
Presents in childhood
Why is PTH elevated in Pseudohypoparathyroidism and not in hypoparathyroidism?
In hypoparathyroidism the glands can’t make PTH
In Pseudohypoparathyroidism the glands can make, problem is with receptors on target organ so PT glands make more PTH
Albright’s heriditary Osteodystrophy (a Pseudohypoparathyroidism disease) signs and symptoms?
Obesity
Short stature
Shortening of metacarpal bones = slanted knuckles
What is it called when you have Albright’s heriditary Osteodystrophy but WITHOUT abnormaliteis in levels of Ca and PTH?
Pseudo-pseudohypoparathyroidism
Mild hypocalcemia treatment?
Oral Ca tablets
If Vit D def - Vit. D tablets
If Mg def - stop any precipitating drugs and replace Mg
If it is post thyroidectomy - repeat calcium levels 24 hours later to see if they stabilize or is treatment needed
When is hypocalcaemia mild or severe?
Mild is less than 2.20 but above 1.9
Severe is less than 1.9
Severe hypocalcaemia treatment?
Medical emergancy
IV Calcium gluconate - initial bolus of 10-20ml of 10% calcium gluconate in 50-100ml of 5% dextrose IV over 10 mins with ECG monitoring
Continue infusions
Treat underlying cause
What form must Vitamin D be given in? and why?
VD needs hydroxylation by kidney, so if patients have severe renal dysfunction should prescribe an already hydroxylated type - calcitro
Levels of hypercalcaemia severity?
<3.0 = asymptomatic and not urgent
3.0-3.5 = May be well tolerated but if rapid rise may be symptomatic and need promp treatment
> 3.5 = Urgernt correction due to risk of coma and dysrhythmia
Causes of acute hypercalcaemia?
1y hyperparathyroidism
Malignancy
Vit D intoxication
Sarcoid/TB
Causes of 1y hyperparathyroidism?
Inherited/Familial
3y cause - renal failure
3 catagories of clinical features of hypercalcaemia?
Renal
GI
MSK
Renal symptoms for hyperC?
Polyuria and polydipsia
Kidney stones
GI symptoms for hyper C?
Anorexia
Nausea and vomiting
Constipation
MSK?
Muscle weakness
Bone pain and osteopenia/porosis depending on severity
What is the saying to help you remember the basic picture of a hypercalcaemic patient?
Bone, stones, groans and psychic moans
What is the neurological effects “psychic moans” of hyper C?
Decreased concentration
Confusion
Fatigue
Stupor/coma
Any CV symptoms for hyper C?
Shortening of QT interval (remember hypo make it lengthen)
Bradycardia
Hypertension
Diagnostic approach for hyper C?
Hx - symptoms of hyperC, meds and FHx
Examination - lymph nodes and concerns about malignancy (breast and lung)
Investigations:
PTH Albumin and Calcium Phosphate Us and Es Consider an ECG
If PTH is normal or high - cause could be?
1y hyperparathyroidism
Familiar
3y hyperparathyroidism - renal failure
If PTH level is low…could be due to?
A malignancy or drug use
1y hyperparathyroidism - tumour causes?
Parathyroid adenoma
4 gland hyperplasia
Very rare - MEN 1 or 2A or parathyroid carcinoma
Investigations if 1y hyperparathyroidism is suspected?
Ultrasound scan
SESTAMIBI / MIBI scan - contrast is taken up by thryoid glands and after 2 hours it will remain in inferior parathyroid gland (affected gland)
What is Familial Hypocalciuric
Hypercalcaemia
Autosomal dominant disorder of the calcium
sensing receptor
PTH may be normal or slightly elevated
Is benign and no therapy indicated
Most-tumour associated
hypercalcaemia is BLANK unless a BLANK where prognosis will be BLANK
1 - mild
2 - endocrine tumour
3 - poor
HyperC management
Rehydration with 0.9% saline 4-6L over 24 hours - consider dialysis if severe renal failure
After rehydration - IV biphosphates
2nd line hyper C management ?
Glucocorticoids - in a lymphoma or other granulomatous disease
Calcitonin - if poor response to bisphosphonates
Calcimimetics
Parathyroidectomy - considered in acute cases with severe hyper C with no other options
