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Endocrine > Clinical Calcium Homeostasis > Flashcards

Clinical Calcium Homeostasis Flashcards

1
Q

Main physiological functions of Ca?

A
  • Bone formation
  • Synaptic transmission
  • Muscle contraction
  • Cell division & growth
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2
Q

How does plasma albumin concentration affect the amount of free calcium? By approximately how much?

A
  • Increased albumin decreases free calcium
  • Decreased albumin increases free calcium
  • Adjust Ca by 0.1mmol/L for each 5g/L reduction in albumin (not 100% sure about that…)
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3
Q

Which gland secretes PTH? From which type of cells?

A
  • Parathyroid glands

- Parathyroid chief cells

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4
Q

What causes the parathyroid gland to secrete PTH?

A

Calcium sensing receptors (CaSR) on the parathyroid gland stimulate the secretion of PTH when extracellular [Ca] is low

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5
Q

Functions of PTH?

A
  • Resorption of calcium into plasma (osteoclasts & renal reabsorption)
  • Secretion of phosphate (PO4)
  • Mediates conversion of vitamin D to its active form (calcitriol synthesis)
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6
Q

What plasma calcium concentration suggests hypocalcaemia?

A

< 2.20 mmol/L

Symptoms usually when < 1.9 mmol/L

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7
Q

What are some symptoms of acute hypocalcaemia?

A
  • Muscle ache
  • Paresthesia
  • Tetany (neuromuscular irritability)
  • Bone pain
  • Seizures
  • Laryngospasm (spasm of vocal cords)
  • Bronchospasm (spasm of bronchial smooth muscle)
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8
Q

What are some cardiac related signs of acute hypocalcaemia?

A
  • Prolonged QT interval
  • Hypotension
  • Heart failure
  • Arrhythmia
  • Papilloedema
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9
Q

What are some neuromuscular clinical signs of acute hypocalcaemia?

A
  • Muscle twitching (fasciculations)
  • Carpopedal spasm (painful cramps in hands & feet)
  • Trousseau’s Sign
  • Chovstek’s Sign
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10
Q

What are some signs / symptoms of chronic hypocalcaemia?

A
  • Ectopic calcification (calcification in soft tissue)
  • Extrapyramidal signs
  • Parkinsonism
  • Dementia
  • Subcapsular cataracts
  • Abnormal dentition / dry skin
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11
Q

What are Trousseau and Chovstek’s signs? What do they suggest?

A
  • Trousseau’s Sign: spasm of the wrist and metacarpal joints after inflating blood pressure cuff around ipsilateral arm for 3 minutes, at above systolic BP
  • Chovstek’s sign: twitching of the facial muscles after tapping over the area of the facial nerve
  • Both indicate hypocalcaemia
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12
Q

Causes of hypocalcaemia?

A
  • Hypoalbuminaemia (commonest)
  • Hypoparathyroidism
  • Total thyroidectomy (iatrogenic)
  • Severe vitamin D deficiency
  • Mg deficiency
  • Cytotoxic drugs
  • Pancreatitis, rhabdomyolysis, large blood transfusions
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13
Q

Investigations for suspected hypocalcaemia?

A

Bloods:
- Ca / PO4 / ALP / vitamin D / PTH / Mg / albumin

U&E
(also look for neck scars)

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14
Q

If there is evidence of hypocalcaemia, high PTH and urea and creatinine are also high, what is the likely diagnosis?

A

Renal failure

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15
Q

If there is evidence of hypocalcaemia, high PTH, normal urea and creatinine, and high vitamin D, what is the likely diagnosis?

A

Pseudohypoparathyroidism

or Ca deficiency

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16
Q

If there is evidence of hypocalcaemia and low PTH what else should be checked? Possible diagnoses?

A

Check Magnesium levels

  • If normal Mg: Hypoparathyroidism
  • If low Mg: Mg deficiency
17
Q

Causes of hypoparathyroidism?

A
  • Agenesis (DiGeorge symptom)
  • Iatrogenic
  • Mg deficiency
  • Cell resistance to PTH (pseudohypoparathyroidism)
18
Q

What is Pseudohypoparathyroidism? Symptoms? How will the bloods look?

A
  • When the bone and kidneys are not sensitive to PTH
  • Obesity, short stature, shortening of the metacarpals and metatarsals
  • Bloods: low Ca, high PO4, high PTH
19
Q

Treatment of severe hypocalcaemia?

A
  • IV calcium gluconate
20
Q

management of hypocalcaemia?

A
  • Oral calcium tablets

- Mg / vitamin D supplements if needed (calcitriol if renal impairment instead of vit D)

21
Q

What blood [Ca] is considered severe hypercalcaemia? What is mild?

A

> 3.5 mmol/L is severe, needs urgent correction

3.0 - 3.5 is mild hyperglycaemia, may be asymptomatic if it has risen slowly

22
Q

Causes of hypercalcaemia?

A
  • Bone metastases (malignancy - PTHrp)
  • Hyperparathyroidism
  • Thyrotoxicosis
  • Elevated calcitriol
  • High vitamin D
  • TB / sarcoidosis
23
Q

Symptoms of hypercalcaemia?

A
  • Painful bones
  • Renal stones
  • Abdominal pain
  • Depression
    (bones, stones, moans, groans)
  • Polydipsia (thirst)
  • Polyuria
24
Q

Investigations for hypercalcaemia?

A 
Bloods:
- PTH
- Ca &amp; albumin
- Vitamin D 
- PTH-rp
Urine Ca
Renal function
25
Q

Investigations for suspected primary hyperparathyroidism??

A
  • Ca, PTH
  • U&Es: check renal function
  • Abdominal imaging: renal calculi
  • DEXA: osteoporosis
  • 24 hour urine collection for calcium: Excl. FHH
  • Vitamin D
26
Q

What is Sestamibi scanning?

A
  • Sestamibi is a small protein which is labeled with the radio-pharmaceutical technetium99, it is injected into the veins of a patient with hyperparathyroidism
  • Gets absorbed by the overactive parathyroid gland. normal parathyroid glands are inactive when there is high calcium, they do not take up the radioactive particles
  • Gamma camera is placed patient’s neck, shows the overactive gland
27
Q

What are the indications for surgery for patients with primary hyperparathyroidism?

A
  • High serum calcium
  • Renal failure / stones
  • < 50 years of age
  • Osteoporosis on DEXA
28
Q

Which pharmaceutical agent causes a fall in PTH? Mechanism?

A

Cinacalcet: mimics the effect of calcium on the calcium sensing receptor on Chief cells, this leads to a fall in PTH and subsequently calcium levels

29
Q

What is Familial Hypocalciuric Hypercalcaemia?

A
  • Autosomal dominant disorder of the calcium sensing receptor (CaSR)
  • Results in high blood [Ca] and low urine [Ca]
  • PTH may be normal or slightly elevated
30
Q

What hereditary form of cancer is closely related to primary hyperparathyroidism?

A
  • Multiple Endocrine Neoplasia (type 1 & 2)

> 95% of M.E.N. type 1 have hyperparathyroidism, 20-30% for type 2

31
Q

First line management of hypercalcaemia?

A
  • Hydration

- After rehydration, intravenous bisphosphonates

Endocrine (30 decks)

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