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Endocrine System > Calcium Pathophysiology and Clinical Aspects > Flashcards

Calcium Pathophysiology and Clinical Aspects Flashcards

1
Q

What are some dietary sources of calcium?

A

Milk, cheese, and other diary
Green leafy vegetables
Soya beans, tofu, nuts, bread and fish with bone

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2
Q

What are the functions of calcium?

A

Bone formation
Cell division and growth
Muscle contraction
Neurotransmitter release

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3
Q

What percentage of calcium is found where?

A

1% in cells
0.1% in extracellular fluid
98.9% in bones

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4
Q

What is the normal range of plasma calcium?

A

2.2-2.6 mmol/l - total
Free calcium is calculated by 0.1mmol/l for each 5g/l reduction in albumin from 40g/l ex. if 2.55mmol/l then free is 2.75

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5
Q

What are some sources for vitamin D?

A

Oily fish, eggs, fortified fat spreads, fortified cereals and some powdered milks

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6
Q

How is parathyroid hormone stimulated?

A

Chief cells respond to change in calcium conc.
There is calcium sensing receptors in parathyroid cells
PTH is secreted in fall of Ca conc.

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7
Q

What are the effects of PTH?

A

Has direct effects that promote reabsorption of calcium from renal tubules and bone
Mediates conversion of Vitamin D from inactive to active form

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8
Q

What are some clinical features of hypocalcaemia?

A

Paraesthesia, muscle twitching, seizures, laryngospasm, and bronchospasm
Cardiac - hypotension, papilledema and prolonged QT interval

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9
Q

When do symptoms for hypocalcaemia usually show?

A

When adjusted serum calcium levels are below 1.9mmol/l

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10
Q

What 2 signs can show hypocalcaemia?

A

Chvostek’s (facial nerve) and Trousseau’s sign

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11
Q

What are some causes of hypocalcaemia?

A

Disruption of parathyroid gland by thyroidectomy
Severe vitamin D deficiency
Mg deficiency
Cytotoxic drug induced hypocalcaemia
Pancreatitis, rhabdomyolysis and large volume blood transfusions

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12
Q

What are some causes of low PTH?

A

Genetic disorders
Post surgical
Autoimmune
Infiltration
Radiation induced
HIV infection

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13
Q

What blood results are used for hypocalcaemia?

A

ECG, serum calcium, PTH, albumin, phosphate, U+E, vitamin D and Mg

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14
Q

What are the investigations for hypocalcaemia?

A

Confirm with adjusted calcium and check PTH
Then if high (appropriate) - check urea and creatine - if normal then check Vit D but if high then renal failure
If low PTH (inappropriate) - Check Mg

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15
Q

What investigation results are predicted in Vit D deficiency?

A

Low total calcium
Low ionised calcium
Low phosphate
High PTH

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16
Q

What investigation results are predicted in hypoparathyroidism?

A

Low total and ionised calcium
High phosphate
Low PTH

17
Q

What could hypoparathyroidism result from?

A

Agenesis
Destruction
Infiltration
Reduced secretion of PTH
Resistance to PTH

18
Q

Describe pseudo-hypoparathyroidism

A

Presents in childhood - heterogeneous disorders defined by target organ which is unresponsive to PTH
Hypocalcaemia, hyperphosphatemia and hypoparathyroidism
Elevated PTH

19
Q

What is the treatment for mild hypocalcaemia?

A

Commence with oral calcium tablets
If post thyroidectomy then repeat calcium 24hrs later
Start vitamin D if deficient
Also if low Mg then replace

20
Q

What is the treatment for severe hypocalcaemia?

A

Medical emergency
Administer IV calcium gluconate
This is repeated until patient is asymptomatic
Treat underlying cause

21
Q

Describe vitamin D replacement if patient has severe renal impairment

A

Alfacalcidol and Calcitriol
As these are the hydroxylated derivatives that would have been hydroxylated in kidneys

22
Q

How much vitamin D should everyone over 5 take every day in winter months?

A

10micrograms a day

23
Q

What is the calcium level of acute hypercalcaemia?

A

<3 mmol/l - often asymptomatic
3-3.5
>3.5 then required urgent correction

24
Q

What are some main causes of hypercalcaemia?

A

Primary hyperparathyroidism
Renal failure
Familial hyperparathyroidism
Malignancy
Vit D intoxication
Chronic granulomatous disorder

25
Q

What are the clinical features of hypercalcaemia?

A

Bones, stones, groans and psychic moans
Polyuria, polydipsia, nephrolithiasis, anorexia, N/V, constipation and muscle weakness
Decreased concentration and shortening of QT interval

26
Q

What blood are done for hypercalcaemia?

A

U+Es, Ca, PO4, Alk phosphate, myeloma screen, serum ACE and PTH

27
Q

Describe the investigations for hypercalcaemia

A

Ca and albumin
Then check PTH
If normal or increased (inappropriate) - primary hyperparathyroidism and familial tertiary hyperparathyroidism
If PTH low - malignancy or drug causes

28
Q

Describe primary hyperparathyroidism

A

More females 3:1
Incidence is 50-60 years
Mostly asymptomatic at diagnosis
Most cases are sporadic with neck irradiation or prolonged lithium use
85% parathyroid adenoma and 15% four gland hyperplasia

29
Q

What are the investigations for primary hyperparathyroidism?

A

Ca, PTH, U+Es, abdominal imaging, DEXA, spot urinary calcium/ creatine ratio, 24hr urinary calcium and Vitamin D
US, $D CT and Sestamibi

30
Q

What are the indications for surgery in primary hyperparathyroidism?

A

Presence of symptoms due to hypercalcaemia
Serum Ca > 0.25mmol/l
Osteoporosis
eGFR <60 or presence of kidney stones
< 50 years

31
Q

What is the medical treatment for primary hyperparathyroidism?

A

Generous fluid intake
Vit D replacement
Cinacalcet - mimics effect of Ca on calcium sensing receptor on chief cells so fall in PTH and Ca levels

32
Q

What are the risks of surgical treatment for primary hyperparathyroidism?

A

Bleeding
Hypocalcaemia
Recurrent laryngeal nerve injury

33
Q

Describe familial hypocalciuric hypercalcaemia

A

Autosomal dominant disorder of Ca sensing receptor
Low levels of urinary calcium
Benign - no therapy
Positive family history
PTH my be normal or elevated

34
Q

Describe prognosis of hypercalcaemia from malignancy

A

Most tumour associated hypercalcaemia is mild
Unless an endocrine tumour then prognosis is poor

35
Q

Describe MEN1

A

Primary hyperparathyroidism, pancreatic and pituitary
95% will have hyperparathyroidism
MENIN mutation
Presents in 20-40s
Multi gland involvement and high recurrence rate

36
Q

Describe MEN Type 2A

A

Medullary thyroid cancer, pheochromocytoma and primary hyperparathyroidism
RET mutation
20-30% have hyperparathyroidism

37
Q

What is the management for hypercalcaemia?

A

Rehydration - 0/9% saline 4-6l
Intravenous bisphosphonates - zoledronic acid
Consider dose reduction in renal impairment

38
Q

What is 2nd line management for hypercalcaemia?

A

Glucocorticoids
Calcitonin
Calcimimetics
Parathyroidectomy

Endocrine System (23 decks)

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