Clinical Calcium Homeostasis Flashcards by Zain Aslam

Functions of Calcium?

Bone formation
Cell division and growth 
Muscle contraction
Neurotransmitter
release

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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

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Normal range of Ca in clinical practice?

2.20-2.60 mmol/l

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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

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Mr Bloggs has a Calcium of 2.55mmol/L, his

albumin is 30g/L. What is his corrected calcium?

2.75mmol/L

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What does acidosis do to calcium?

Increases levels of free Ca2+ predisposing to hypercalcaemia

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What do chief cells in parathyroid glands respond to?

Directly to changes in calcium conc.

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Alterations in ECF calcium levels are transmitted into the parathyroid cells via…

Calcium sensing receptor (CaSR)

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PTH is secreted in response to..?

A fall in calcium

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What does PTH do?

Promotes reabsorption of Ca from renal tubules and bone

Mediates conversion of Inactive Vit. D to active

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What levels of calcium indicate hypocalcemia?

<2.20 mmol/l

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What 2 categories of symptoms does acute hypocalcemia cause?

Neuromuscular

Cardiac

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Name some neuromuscular symptoms of acute hypocalcaemia.

Paresthesia 
Muscle twitching
Carpopedal spasm 
Trousseau's and Chovstek's sign 
Seizures
Broncho and Laryngo spasms

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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

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What is Chovstek’s sign?

Tap facial nerve and lip will twitch or facial muscles will spasm (depending on severity of hypocalcaemia)

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What is the cardiac symptoms of acute hypocalcaemia?

Prolonged QT interval 
Hypotension
Heart failure
Arrythmia
Papilloedema

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Symptoms of chronic hypocalcaemia?

Ectopic calcification 
Extrapyramidial signs
Parkinsonism
Dementia
Dry skin

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Causes of hypocalcaemia with a low PTH (1y)?

Thyroid surgery
Genetic
Autoimmune
Infiltration
Radiation induced destruction of PT gland

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Causes of hypocalcaemia with a high PTH (2y)?

Vit. D deficiency
Pseudohypoparathyroidism
Magnesium deficiency
Renal disease

Acute pancreatitis
Acute respiratory alkalosis

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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

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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