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MBChB - Y2 - Endocrine > Clinical Calcium Homeostasis > Flashcards

Clinical Calcium Homeostasis Flashcards

1
Q

What are the functions of calcium?

A

Bone formation

Cell division and growth

Muscle contraction

Neurotransmitter release

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2
Q

What are some dietary sources of calcium?

A

Milk, cheese and other dairy foods

Green leay vegetables (broccoli, cabbage, not spinnach)

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3
Q

Where does most of the plasma go once it enters the body?

A

Out again (as faeces)

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4
Q

How does the level of albumin affect the level of calcium?

A

Increased albumin decreases free calcium

Decreased albumin increases free calcium

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5
Q

How do we calculate the calcium concentration from the concentration of albumin?

A

– Adjust Ca2+ by 0.1mmol/l for each 5g/l reduction in albumin from 40g/l

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6
Q

How does acidosis affect calcium?

A

Acidosis increases ionised calcium - predisposing to hypercalcaemia

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7
Q

What are the sources of vitamin D?

A

Oily fish - salmon, sardines and mackrel

Eggs

Fortified fat spreads

Fortified breakfast cereals

Some powdered milks

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8
Q

What groups are at risk of vitamin D deficiency?

A

Children

Pregnant woman

People in nursing homes / constitutions

People of colour

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9
Q

When is PTH released?

A

In response to a fall in calcium

Alterations in ECF calcium levels are transmitted into the parathyroid cells via calcium sensing receptor (CaSR)

Chief cells respond directly to changes in calcium concentrations

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10
Q

What are the effects of parathyroid hormone?

A

Promote reabsorption of calcium from the renal tubes and bone

PTH mediates the covnersion of vitamin D from its inactive form to its active form

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11
Q

What is the metabolic process of forming the active form of vitamin D?

A

25 (OH) vitamin D (inactive) + 25(OH) alpha hydroxylase = 1,25 (OH)2 vitamin D (active)

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12
Q

What is the reference range for serum calcium?

A

2.20 - 2.60

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13
Q

What are the acute features of hypocalcaemia?

A
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14
Q

What are chovstek’s sign and trosseau’s sign?

A

Chvostek’s sign is the twitching of the facial muscles in response to tapping over the area of the facial nerve.

Trousseau’s sign is carpopedal spasm caused by inflating the blood-pressure cuff to a level above systolic pressure for 3 minutes

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15
Q

What are the chronic features of hypocalcaemia?

A
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16
Q

What are the causes of hypocalcaemia?

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 (such as omeprazole)

Cytotoxic drug-induced hypocalcaemia

Pancreatitis, rhabdomyolysis and large volume blood tranfusions

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17
Q

What effect does respiratory alkalosis have on calcium?

A

Causes hypocalcaemia

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18
Q

What are relevant things to note when making a diagnosis of hypocalcaemia?

A

Neck surgery / scars

Diet

Medications

Autoimmune disroders

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19
Q

What are the low PTH versus high PTH causes of hypocalcaemia?

A

Low PTH is hypoparathyroidism:

Causes include:

Genetic disorders

Post - surgical (thyroidectomy, parathyroidectomy, radical neck dissection)

Infiltration of the parathyroid gland (granulomatous, iron overload, metastases)

Hungry bone syndrome (post parathyroidectomy)

HIV infection

High PTH (secondary hyperparathyroidism) - this is in response to low calcium

Vitamin D deficiency

Pseudoparathyroidism

Hypomagnesia

Renal disease

Acute pancreatitis

Acute respiratory alkalosis

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20
Q

What are the relevant investigations for hypocalcaemia?

A

ECG (Prolonged QT, arrhythmias)

Serum calcium

Albumin

Phosphate

PTH

U and E’s

Vitamin D

Magnesium

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21
Q

How do levels of phosphate and PTh vary between vitamin D deficiency and hypoparathyroidism?

A

Vitamin D: Phosphate is low and PTH is high

Hypoparathyroidism: Phosphate is high ad PTH is low

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22
Q

What are the causes of hypoparathyroidism?

A

Agenesis

Destruction (neck surgery or autoimmune disease)

Infiltration (haemochromatosis or Wilson’s disease)

Reduced secretion of PTH (neonatal hypocalcaemia, hypomagnesia)

Resistance to PTH

23
Q

What is pseudohypoparathyroidism?

A

Target organ (kidney and bone) does not respond to PTH

24
Q

What are the blood tests for pseudohypoparathyroidism?

A

Hypocalcaemia

Hyperphosphataemia

Elevated PTH

25
Q

What are the clinical features of pseudohypoparathyroidism?

A

Albrights hereditary osteodystrophy (AHO)

Obesity

Short stature

Shortening of the metacarpal bones

26
Q

What is treatment of milf hypocalcaemia?

asymptomatic - greater than 1.9 mmol/l

Reference range is 2.2-2.6

A

Oral calcium tablets

Post thyroidectomy - repeat calcium 24 hours later

If vitamin D deficient - start vitamin D

If low magnesium, stop any precipitating drug and replace magnesium

27
Q

What is the treatment for severe hypocalcaemia?

A

This is a medical emergency

Administer IV calcium gluconate

Initial bolus (10-20ml 10% calcium gluconate in 50-100ml of 5% dextrose IV over 10 minutes with ECG monitoring)

Calcium gluconate infusion

Treat the underlying cause

28
Q

How do we increase the amount of vitamin D in a patient who has severe renal impairment?

A

Alfacalcidol

Or

Calcitrol

Vitamin D requires hydroxylation by the kidney to its active form, therefore the hydroxylated derivatives alfacalcidol or calcitriol should be prescribed if patients with severe renal impairment require vitamin D therapy

29
Q

What are the parathyroid mediated causes of hypercalcaemia?

A

Either MEN 1 or MEN 2A

30
Q

What are the non-parathyroid mediated causes of hypercalcaemia?

A
31
Q

What medicatinos can cause hypercalcaemia?

A

Thiazide like diuretics

Lithium

Theophyline toxicity

32
Q

What are the miscellaneous reasons for hypercalcaemia?

A

Hyperthyroidism

Acromegaly

Pheochromocytoma

Adrenal insuficiency

Immobilisation

Parenteral nutrition

33
Q

What systems does hypercalcaemia affect?

A

Bones, stones, groans and psychic moans

Clinical features come under 5 categories

Renal, Gastrointestinal, MSK, Neurological and Cardiovascular

34
Q

What are the renal manifestations of hypercalcaemia?

A

Polyuria

Polydipsia

Nephrolithiasis (kidney stones)

35
Q

What are the GI manifestations of hypercalcaemia?

A

Anorexia

Nausea and vomiting

Bowel hypomobility and constipation

36
Q

What are the MSK manifestations of hypercalcaemia?

A

Muscle weakness

Osteoporosis

37
Q

What are the neurological clinical features of hypercalcaemia?

A

Decreased concentration, confusion

38
Q

What are the CVS manifestations of hypercalcaemia?

A

Short QT

Bradycardia

Hypertension

39
Q

What arew the important considerations when making a diagnosis of hypercalcaemia?

A

Examine the lymph nodes - concerns about malignancy

40
Q

What are the important investigations when dealing with hypercalcaemia?

A

U and E’s

Calcium

Phosphate

Alk Phosphate

Myeloma screen

Serum ACE (this is to check for sarcoidosis which is a non-parathyroid cause of hypercalcaemia)

PTH

41
Q

What are the causes of hypercalcaemia when there is normal/increased PTH?

A

Primary hyperparathyroidism

Familial hypocalciuric hypercalcaemia

Tertiary hypercalcaemia (renal failure)

42
Q

What causes hypercalcaemia when PTH is low?

A

Malignancy or Drugs

43
Q

What are the causes of hyperparathyroidism?

A

Most cases are sporadic but has been associated with neck irradiation or prolonged lithium use

  • 85% parathyroid adenoma
  • 15% four gland hyperplasia
  • <1% MEN type 1 or 2A
  • <1% parathyroid carcinoma
  • Often present for years prior to diagnosis
44
Q

What are common presentatinos of primary hyperparathyroidism?

A

Nephrolithiasis

Bone disease

Asymptomatic

45
Q

What are the relevant investigations for hyperparathyroidism?

A

Calcium, PTH

U and E’s: Check renal function (tertiary hyperparathyroidism - renal failure)

Abdominal imaging: Renal calculi

Dexa: Osteoporosis

24 hour urine collection for calcium - to exclude familial hypocalciuiric hypercalcaemia

Vitamin D

46
Q

What are the relevant imaging techniques for hyperparathyroidism?

A

Parathyroid ultrasound

SESTAMIBI

47
Q

What are the indications for surgical treatment in primary hyperparathyroidism?

A

Presence of symptoms due to hypercalcaemia

Serum calcium: 0.25 mmol/L above the upper limit of normal

Skeletal: Osteoporosis on DEXA

Renal: eGFR less than 60 or presence of kidney stones

Age: Less than 50

48
Q

What is the treatment for primary hyperparathyroidism?

A

– Generous fluid intake

– Cinacalcet (acts as a calcimetic, i.e. mimics the effect of calcium on the calcium sensing receptor on Chief cells, this leads to a fall in PTH and subsequently calcium levels)

49
Q

What is familial hypocalciuric hypercalcaemia?

A

Autosomal dominant disorder of the calcium sensing receptor

Benign, no therapy indicated

Positive family history, screen young family

members for diagnosis.

PTH may be normal or slightly elevated

No evidence of abnormal parathyroid tissue on ultrasound or isotope scan

50
Q

Give two examples of malignancy that can cause hypercalcaemia

A

Humoural hypercalcaemia of malignancy

The causal agent is PTHrP

Features in squamous cell cancer (including lung), renal, ovarian, endometrial and breast cancer

Local osteolytic hypercalcaemia

Causal agent is cytokines, chemokines and PTHrP

51
Q

What multple endocrine neoplasias result in hyperparathroidism?

A

MEN1 - >95% of MEN 1 will have hyperparathyroidism

MEN type 2A - 20-30 % of MEN2A have hyperparathyroidism

52
Q

What is the management of hypercalcaemia?

A
53
Q

What is second line management for hypercalcaemia?

A
54
Q

What are the drugs that can cause hypocalcaemia?

A

MBChB - Y2 - Endocrine (25 decks)

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