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ZA - Endocrine System > Clinical Calcium Homeostasis > Flashcards

Clinical Calcium Homeostasis Flashcards

1
Q

Functions of Calcium?

A 
Bone formation
Cell division and growth 
Muscle contraction
Neurotransmitter
release
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2
Q

What proportion of Ca is bound in plasma and to what?

A

45% bound mainly to albumin
10% in non-ionised or complexed to other molecules
45% is ionised - biologically important

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3
Q

Normal range of Ca in clinical practice?

A

2.20-2.60 mmol/l

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4
Q

How do we calculate free calcium?

A

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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5
Q

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

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

A

2.75mmol/L

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6
Q

What does acidosis do to calcium?

A

Increases levels of free Ca2+ predisposing to hypercalcaemia

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7
Q

What do chief cells in parathyroid glands respond to?

A

Directly to changes in calcium conc.

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8
Q

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

A

Calcium sensing receptor (CaSR)

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9
Q

PTH is secreted in response to..?

A

A fall in calcium

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10
Q

What does PTH do?

A

Promotes reabsorption of Ca from renal tubules and bone

Mediates conversion of Inactive Vit. D to active

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11
Q

What levels of calcium indicate hypocalcemia?

A

<2.20 mmol/l

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12
Q

What 2 categories of symptoms does acute hypocalcemia cause?

A

Neuromuscular

Cardiac

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13
Q

Name some neuromuscular symptoms of acute hypocalcaemia.

A 
Paresthesia 
Muscle twitching
Carpopedal spasm 
Trousseau's and Chovstek's sign 
Seizures
Broncho and Laryngo spasms
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14
Q

What is Trousseau’s sign?

A

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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15
Q

What is Chovstek’s sign?

A

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

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16
Q

What is the cardiac symptoms of acute hypocalcaemia?

A 
Prolonged QT interval 
Hypotension
Heart failure
Arrythmia
Papilloedema
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17
Q

Symptoms of chronic hypocalcaemia?

A 
Ectopic calcification 
Extrapyramidial signs
Parkinsonism
Dementia
Dry skin
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18
Q

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

A 
Thyroid surgery
Genetic
Autoimmune
Infiltration
Radiation induced destruction of PT gland
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19
Q

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

A

Vit. D deficiency
Pseudohypoparathyroidism
Magnesium deficiency
Renal disease

Acute pancreatitis
Acute respiratory alkalosis

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20
Q

Diagnostic approach for hypocalcaemia?

A

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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21
Q

Why would we check PTH?

A

See if its a 1y or 2y cause

22
Q

If PTH shows as high - 2y cause - what would you check next? Why?

A

Urea and Creatine - if low it is renal failure

23
Q

U&Es are normal, what else can we check?

A

Vitamin D levels if its a deficiency

24
Q

If PTH was low or normal - indicating a 1y cause - what would we check for and why?

A

Magnesium - if low its a deficiency

If normal it’s a problem with the glands - hypoparathyroidism OR a rare calcium sensing receptor defect

25
Q

What is Pseudohypoparathyroidism, when does it present?

A

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

26
Q

Why is PTH elevated in Pseudohypoparathyroidism and not in hypoparathyroidism?

A

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

27
Q

Albright’s heriditary Osteodystrophy (a Pseudohypoparathyroidism disease) signs and symptoms?

A

Obesity
Short stature
Shortening of metacarpal bones = slanted knuckles

28
Q

What is it called when you have Albright’s heriditary Osteodystrophy but WITHOUT abnormaliteis in levels of Ca and PTH?

A

Pseudo-pseudohypoparathyroidism

29
Q

Mild hypocalcemia treatment?

A

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

30
Q

When is hypocalcaemia mild or severe?

A

Mild is less than 2.20 but above 1.9

Severe is less than 1.9

31
Q

Severe hypocalcaemia treatment?

A

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

32
Q

What form must Vitamin D be given in? and why?

A

VD needs hydroxylation by kidney, so if patients have severe renal dysfunction should prescribe an already hydroxylated type - calcitro

33
Q

Levels of hypercalcaemia severity?

A

<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

34
Q

Causes of acute hypercalcaemia?

A

1y hyperparathyroidism
Malignancy
Vit D intoxication
Sarcoid/TB

35
Q

Causes of 1y hyperparathyroidism?

A

Inherited/Familial

3y cause - renal failure

36
Q

3 catagories of clinical features of hypercalcaemia?

A

Renal
GI
MSK

37
Q

Renal symptoms for hyperC?

A

Polyuria and polydipsia

Kidney stones

38
Q

GI symptoms for hyper C?

A

Anorexia
Nausea and vomiting
Constipation

39
Q

MSK?

A

Muscle weakness

Bone pain and osteopenia/porosis depending on severity

40
Q

What is the saying to help you remember the basic picture of a hypercalcaemic patient?

A

Bone, stones, groans and psychic moans

41
Q

What is the neurological effects “psychic moans” of hyper C?

A

Decreased concentration
Confusion
Fatigue
Stupor/coma

42
Q

Any CV symptoms for hyper C?

A

Shortening of QT interval (remember hypo make it lengthen)
Bradycardia
Hypertension

43
Q

Diagnostic approach for hyper C?

A

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
44
Q

If PTH is normal or high - cause could be?

A

1y hyperparathyroidism

Familiar

3y hyperparathyroidism - renal failure

45
Q

If PTH level is low…could be due to?

A

A malignancy or drug use

46
Q

1y hyperparathyroidism - tumour causes?

A

Parathyroid adenoma
4 gland hyperplasia

Very rare - MEN 1 or 2A or parathyroid carcinoma

47
Q

Investigations if 1y hyperparathyroidism is suspected?

A

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)

48
Q

What is Familial Hypocalciuric

Hypercalcaemia

A

Autosomal dominant disorder of the calcium
sensing receptor

PTH may be normal or slightly elevated

Is benign and no therapy indicated

49
Q

Most-tumour associated

hypercalcaemia is BLANK unless a BLANK where prognosis will be BLANK

A

1 - mild
2 - endocrine tumour
3 - poor

50
Q

HyperC management

A

Rehydration with 0.9% saline 4-6L over 24 hours - consider dialysis if severe renal failure

After rehydration - IV biphosphates

51
Q

2nd line hyper C management ?

A

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

ZA - Endocrine System (21 decks)

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