Clinical Calcium Homeostasis Flashcards Preview

Year 2 - Endocrine System > Clinical Calcium Homeostasis > Flashcards

Flashcards in Clinical Calcium Homeostasis Deck (15)
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1
Q

How do we calculate free calcium in clinical practice

A
  • Increased albumin decreases free calcium
  • Decreased albumin increases free calcium
  • Adjust Ca2+ by 0.1mmol/L for each 5g/L reduction in albumin from 40g/L
2
Q

What groups are at risk of vitamin D deficiency?

A
  • Infants and children aged < 5 years
  • Older people aged > 65 years
  • Pregnant and breastfeeding women, particularly
  • Individuals with darker skin
3
Q

Descibe the role of parathyroid hormone in maintaining homeostasis

A
  • Parathyroid hormone is key to calcium homeostasis
  • In response to a fall in calcium, parathyroid chief cells respond directly by detecting caclium ECG levels via calcium-sensing receptor (CaSR)
  • Increased parathyroid hormone is then secreted
4
Q

Apart from maintaining plasma levels of calcium, what else does parathyroid hormone do?

A
  • Promotes reabsorption of calcium from renal tubules and bone
  • Mediates the conversion of vitamin D from its inactive form to its active form
5
Q

Symptoms of hypocalcaemia typically develop when adjusted serum calcium levels fall below ____ mmol/L

A

1.9

(however this threshold does vary and is dependent on the rate of fall)

6
Q

What are some clinical features of hypocalcaemia?

A

Clinical features: (SPASMODIC)

  • Spasms (carpopedal spasm)/Trousseau’s sign (tetany in response to a tightened BP cuff: the wrist and fingers flex and draw together)
  • Paresthesia
  • Anxiety
  • Seizures
  • Muscle twitching
  • Orientation impaired (time, place and person) and confusion
  • Dry skin
  • Impetigo herpetiformis
  • Chvostek’s sign (the corner of the mouth twitches when the facial nerve is tapped over the parotid)
7
Q

What are the causes of hypocalcaemia due to low parathyroid hormone?

A
  • Genetic disorder
  • Autoimmune
  • Post-surgical: i.e. thyroidectomy, parathyroidectomy,
8
Q

What are the causes of hypocalcaemia due to high parathyroid hormone?

A
  • Vitamin D deficiency
  • Hypomagnesaemia
  • Acute pancreatitis
  • Acute respiratory alkalosis
  • Renal disease
9
Q

State briefly the diagnostic approach to hypocalcaemia

A
  • History
  • Examination
  • Investigations
10
Q

In the diagnostic appraoch to hypocalcaemia, what do we ask about in the history?

A

Ask about:

  • Symptoms
  • Autoimmune disorders
  • Neck surgery
  • Medication
  • Family history
  • Calcium and vitamin D intake
11
Q

In the diagnostic appraoch to hypocalcaemia, what do we look for on examination?

A

Look for:

  • Neck scars
12
Q

In the diagnostic appraoch to hypocalcaemia, what investigations do we perform?

A
  • ECG: prolonged QT interval
  • Serum calcium
  • Albumin
  • Phosphate
  • PTH
  • U+Es
  • Vitamin D
  • Magnesium
13
Q

Look at this:

A
14
Q

What is the treatment for “mild” hypocalcaemia (asymptomatic, >1.9mmol/L)

A
  • Oral calcium tablets (with daily plasma calcium levels)
  • Vitamin D tablets if deficient
  • Stop any precipitating drugs and replace Mg2+ if low
15
Q

What is the treatment for “severe” hypocalcaemia (symptomatic, <1.9mmol/L)

A
  • 10-20ml 10% calcium gluconate in 50-100 ml of 5% dextrose IV over 10 minutes with ECG monitoring
  • Treat the underlying cause