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2ND YEAR SYSTEMS: Diabetes and Endocrinology > Clinical calcium homeostasis > Flashcards

Clinical calcium homeostasis Flashcards

1
Q

Dietary sources of calcium

A

milk, cheese and other dairy foods

green leafy vegetables– such as broccoli, cabbage and okra, but not spinach

soya beans

Tofu

nuts

bread and anything made with fortified flour

fish where you eat the bones– such as sardines and pilchards

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2
Q

Functions of calcium (4)

A

Bone formation

Cell division and growth

Muscle contraction

Neurotransmitter release

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3
Q

Normal range of Calcium in the blood in clinical practice

A

2.20 - 2.60 mmol/l

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4
Q

What effect does increased albumin have on free calcium

A

free calcium decreases

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5
Q

How does acidosis lead to hypercalcaemia

A

acidosis increases ionised (free) calcium

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6
Q

Groups at risk of vitamin D deficiency

A

infants and children

pregnant and breastfeeding women, particularly teenagers and young women

Elderly

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7
Q

What types of cells respond directly to changes in calcium concentrations

A

Parathyroid Chief cells

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8
Q

Alterations in ECF Ca2+ levels are transmitted into the parathyroid cells via which receptor

A

Calcium-sensing receptor

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9
Q

Which hormone is secreted in response to a fall in calcium? what is it’s direct effect

A

Parathyroid hormone

promotes reabsorbtion of calcium from renal tubules & bone into the blood

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10
Q

What bone problems can persistent high PTH level lead to

A

Osteopenia

Osteoporosis

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11
Q

How does PTH affect vitamin D

A

It mediates the conversion of vit D from its inactive to active form

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12
Q

Where does vitamin D activation occur?

A

In the kidney

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13
Q

Pathway of vitamin D

A

Sunlight/diet

converted first into vit d 25-hydroxylase in the liver (inactive form)

Moves to kidney - here it becomes activated. It then moves to the gut

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14
Q

Hypocalcaemia clinical range

A

Serum calcium <2.20

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15
Q

Clinical features of hypocalcaemia

A

Neuromuscular irritability (tetany)

Spasms - carpopedal spasm

Anxious/irritable

cardiac problems (arrhythmias, HF, hypotension), papilloedema

Symptoms typically develop when serum calcium <1.9mmol/L

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16
Q

Clinical signs of hypocalcaemia

A

Chovstek’s sign

Trosseau’s sign

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17
Q

What is Trosseau’s sign/how do you test it?

A

carpopedal spasm caused by inflating the blood-pressure cuff to a level above systolic pressure for 3 minutes

Hand curls inwards at wrist

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18
Q

What is Chovstek’s sign/how do you test it?

A

Ask patient to relax facial nerves. Tap the facial nerve just anterior to earlobe or below the zygomatic arch + corner of mouth

+ response = twitching of the lip at the corner of the mouth to spasm of all facial muscles, depending on severity of hypocalcaemia

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19
Q

What surgery can cause damage to the parathyroid gland?

A

total thyroidectomy

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20
Q

Causes of hypocalcaemia (6)

A

Disruption of parathyroid gland due to total thyroidectomy. May be temporary or permanent

Following selective parathyroidectomy (usually transient & mild)

Severe vitamin D deficiency

Mg2+ deficiency

Cytotoxic drug-induced hypocalcaemia

Pancreatitis, rhabdomyolysis and large volume blood tranfusions

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21
Q

Most common causes of low PTH

A

Gentic disorders

Autoimmune

HIV infection

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22
Q

Most common causes of high PTH - secondary hyperparathyroidism in response to hypocalcaemia

A

Vit D deficiency

Pseudohypoparathyroidism

Hypomagnesemia

Renal disease

Acute pancreatitis

Acute respiratory alkalosis

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23
Q

Most common drugs causing hypocalcaemia

A

Inhibitors of bone resorption - bisphosphonates

24
Q

Investigations done to diagnose hypocalcaemia (8)

A 
ECG
Serum calcium
Albumin
Phosphate
PTH
U&amp;Es - check if PTH is high
Vitamin D
Magnesium - check if PTH is low or normal
25
Q

What is the link between serum albumin and calcium?

A

If serum albumin levels fall so do the calcium levels

26
Q

If magnesium levels are normal but you have low/normal PTH then what are the probable diagnoses

A

hypoparathyroidism or calcium sensing receptor defect

27
Q

If you have high PTH and high levels of creatinine what is the probable diagnosis

A

Renal failure

28
Q

Vitamin D deficiency:

what results would you expect for total calcium, ionised calcium, phosphate and PTH

A

Total calcium = low

Ionised calcium = low

Phosphate = low

PTH = high (due to low Ca2+)

29
Q

Link between PTH and calcium

A

Parathyroid hormone is secreted by the parathyroid glands and is the most important regulator of blood calcium levels

Low calcium levels stimulate PTH secretion, whereas high calcium levels prevent the release of PTH

30
Q

Function of vitamin D

A

Vitamin D promotes calcium absorption in the gut and maintains blood calcium levels to enable normal mineralization of bone and prevent abnormally low blood calcium levels that can then lead to tetany

So increase in vit d => increase in Ca2+
less vit D = less Ca2+ being absorbed

31
Q

Hypoparathyroidism:

What results would you expect for total calcium, ionised calcium, phosphate and PTH?

A

Total calcium = low

Ionised calcium = low

Phosphate = High (low PTH means low calcium levels so serum phosphorus increases as its function is to help the body absorb and utilise calcium

PTH = low

32
Q

How might hypoparathyroidism result (5)

A

Agenesis (DiGeorge syndrome - underdeveloped parathyroid glands)

Destruction (neck surgery, autoimmnue disease)

Infiltration (haemochromatosis or Wilson’s disease)

Reduced secretion of PTH

Resistance to PTH

33
Q

What is pseudohypoparathyroidism?

A

Group of diseases defined by target organ unresponsiveness to PTH

Presents in childhood

34
Q

What is pseudohypoparathyroidism characterised by?

A

Hypocalcaemia

Hyperphophataemia

Elevated PTH (not binding to target organs so staying in blood)

35
Q

What are symptoms of Albright’s heriditary Osteodystrophy

A

Obesity, short stature, shortening of the metacarpal bones

36
Q

What is it called if you have AHO alone without abnormalities of calcium or parathyroid hormone

A

pseudo-pseudohypoparathyroidism

37
Q

Treatment of mild hypocalcaemia (asymptomatic >1.9 mmol/L)

A

Commence oral calcium tablets

If post thyroidectomy repeat calcium 24 hours later

If vit D deficient, start vitamin D

If low Mg2+, stop any precipitating drug and replace Mg2+

38
Q

What types of drugs can cause hypomagnesemia

A

antibiotics

chemotherapeutic agents

diuretics

proton-pump inhibitors

39
Q

Treatment of severe hypocalcaemia emergency

A

Administer IV calcium gluconate - repeat if needed

ECG monitoring

Treat underlying cause like respiratory alkalosis

40
Q

In patients with severe renal impairment require vitamin D therapy what should you give them and why?

A

Alfacalcidol or calcitriol

These are already in active form

In renal disease kidney isn’t functioning properly so can’t hydroxylate vitamin D into active form

41
Q

A calcium level of >3.5 mmol/L requires what?

A

Urgent correction due to risk of dysrhthmia and coma

42
Q

Main causes of hypercalcaemia (2)

A

Primary hyperparathyroidism

Malignancy

43
Q

Clinical features of hypercalcaemia (6)

A 
Polyuria
Thirst
Anorexia
Nausea + vomiting
Muscle weakness
Constipation
44
Q

Phrase that helps you remember hypercalcaemia symptoms

A

Bones, stones, groans + psychic mones

Renal stones
Muscle weakness
Confusion/decreased concentration
Depression

45
Q

Example patient presenting with hypercalcaemia of malignancy

A 
Weight loss
Changed bowel habit
Low PTH 
High Calcium
Heavy smoker + chronic cough
46
Q

Investigations for Hypercalcaemia (8)

A

U&Es
Ca2+
PO4 - increased points to cancer diagnosis
Alk phos
Myeloma screen
Serum ACE
PTH - if high then points to hyperparathyroidism, if low => cancer

consider ECG

47
Q

Most common causes of Primary hyperparathyroidism

A

Adenoma

Hyperplasia of all glands

48
Q

Investigations for primary hyperparathyroidism (6)

A

Ca2+ and PTH

U+E

Abdominal imaging

DEXA for osteoporosis

24hr urine collection for Ca2+

Vit D

Parathyroid USS, CT, PET

49
Q

When would a patient be indicative for parathyroid surgery?

A

If patient is <50, has osteoporosis on DEXA, normal serum calcium, kidney stones, has symptoms of hypercalcaemia

50
Q

Treatment of primary hyperparathyroidism

A

Parathyroid surgery

Medical management - generous fluid intake, Cinacalcet - mimics effect of Ca2+ on calcium sensing receptor on Parathyroid chief cells causing fall in PTH and subsequently low Ca2+ levels)

51
Q

What is Familial Hypocalciuric

Hypercalcaemia

A

Autosomal dominant inherited disorder that causes hypercalcemia and hypocalciuric (low levels of urinary Ca2+)

Affects the calcium sensing receptor

Positive family history, screen young family members for diagnosis.

No evidence of abnormal parathyroid tissue on ultrasound or isotope scan

52
Q

Multiple Endocrine

Neoplasia type 1 (MEN-1)

A

Main causes: Primary hyperparathyroidism (>95%) Pancreatic or Pituitary

MENIN mutation on chromosome 11

53
Q

Multiple Endocrine

Neoplasia type 2 (MEN-2)

A

Associated with:
Medullary thyroid cancer
Phaeochromocytoma
Primary hyperparathyroidism

RET mutation

54
Q

What are Multiple Endocrine

Neoplasias

A

Syndromes where there are functioning hormone-producing tumours in multiple organs, these are:
MEN-1
MEN-2

55
Q

Management of hypercalcaemia

A

Rehydration - monitor for fluid overload, consider dialysis if severe renal failure

after rehydration - IV bisphophonates

56
Q

2nd line management of hypercalcaemia

A

Glucocorticoids

Calcitonin

Calcimimetics

Parathyroidectomy

2ND YEAR SYSTEMS: Diabetes and Endocrinology (21 decks)

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