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Pathology (Guide) > Chemical Pathology - Calcium > Flashcards

Chemical Pathology - Calcium Flashcards

1
Q

Where is 99% of calcium found?

A

Stored in the skeleton (calcium reservoir)

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2
Q

What is the breakdown of free calcium in the body?

A
  • 45% = ionised (free, biologically active form)
  • 50% bound to albumin (affected by albumin level, therefore need to use corrected calcium)
  • 5% bound to globulins + other ions
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3
Q

What are the two hormones involved in calcium metabolism?

A
  • Parathyroid hormone (PTH)
  • Calcitriol
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4
Q

What does Parathyroid do in relation to calcium?

A

Increases calcium in the blood

  • Increases tubular 1α hydoxylation of Vitamin D (25(OH)D)
  • Mobilises calcium from bone through osteoclast activation
  • Increases renal calcium reabsorption
  • Increases renal phosphate excretion
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5
Q

What does calcitriol (1,25(OH)2D) do in relation to calcium?

A

Increases calcium in the blood
- Increases calcium and phosphate absorption from the gut
- Bone remodelling

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6
Q

What hormone decreases calcium levels in the blood?

A

Calcitonin

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7
Q

What is the metabolism of Vitamin D?

A
  • 7-dehydrocholesterol converts to cholecalciferol via sunlight
  • Cholecalciferol is found in Vitamin D3 tablets + Fish oils
  • Cholecalciferol is converted to calciferol (25-OH D3) by 25-hydroxylase in the liver
  • Calciferol gets converted to Calcitriol (1,25(OH)2D) via 1α hydroxylase
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8
Q

What is the process of calcium control in the body?

A
  • Decreased calcium causes PTH release from PTH gland
  • Bone resorption occurs in osteoclsts from calcium stored in bone (Increases Ca in blood - PO4 increases)
  • Ca reuptake in the kidney is increased (PO4 decreased) - Ca also excreted in urine
  • PTH triggers 1α dehydroxylase activity, converting calciferol to calcitriol
  • Calcitriol worse in the gut to increase Ca + PO4 uptake
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9
Q

Which conditions have the highest to lowest calcium concentrations?

(Primary Hyperparathyroidism, Secondary Hyperparathyroidism, Parathyroud Carcinoma, Osteomalacia, Osteoporosis)

A
  1. Parathyroid Carcinoma
  2. Primary Hyperparathyroidism
  3. Osteoporosis
  4. Secondary Hyperparathyroidism
  5. Osteomalacia
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10
Q

What is the defect in primary hyperparathyroidism?

A

Intrinsic problem with parathyroid gland, causing increased PTH

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11
Q

What are the blood results of primary hyperparathyroidism?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Increased
  • PO4: Decreased
  • PTH: Increased/Normal
  • ALP: Increased/Normal
  • Vit D: Normal
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12
Q

What is the defect in secondary hyperparathyroidism?

A

Pathology outside parathyroid gland: stimulation of parathyroid gland to produce more PTH

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13
Q

What are the blood results of secondary hyperparathyroidism?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Decreased
  • PO4: Increased
  • PTH: Increased
  • ALP: Increased
  • Vit D: Decreased/Normal
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14
Q

What is the defect in tertiary hyperparathyroidism?

A

Autonomous PTH secretion

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15
Q

What are the blood results of tertiary hyperparathyroidism?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Increased/Normal
  • PO4: Decreased/Increased
  • PTH: Increased
  • ALP: Increased/Normal
  • Vit D: Decreased/Normal
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16
Q

What is the defect in hypoparathyroidism?

A

Low levels of PTH

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17
Q

What are the blood results of hypoparathyroidism?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Decreased
  • PO4: Increased
  • PTH: Decreased
  • ALP: Decreased/Normal
  • Vit D: Normal
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18
Q

What is the defect in Rickets/osteomalacia?

A

Vitamin D deficiency

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19
Q

What are the blood results of rickets/osteomalacia?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Decreased
  • PO4: Decreased
  • PTH: Increased
  • ALP: Increased
  • Vit D: Decreased
20
Q

What is the defect in Paget’s disease?

A

Re-modelling of bone

21
Q

What are the blood results of Paget’s disease?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Normal
  • PO4: Normal
  • PTH: Normal
  • ALP: Increased
  • Vit D: Normal
22
Q

What is the defect in osteoporosis?

A

Bone loss

23
Q

What are the blood results of osteoporosis?

(Ca, PO4, PTH, ALP, Vit D)

A
  • Ca: Normal
  • PO4: Normal
  • PTH: Normal
  • ALP: Normal
  • Vit D: Normal
24
Q

What are some causes (and their prevalence) of primary hyperparathyroidism?

A
  • Single parathyroid adenoma (80%)
  • Hyperplasia + multple adenomas (15%)
  • Carcinomas (mostly non-functional) (0.5%)
  • MEN1 (adenoma) + MEN2 (hyperplasia)
25
Q

What are some causes of secondary hyperparathyroidism?

A
  • CKD
  • Vitamin D deficiency
  • Malabsorption syndromes
  • PTH resistance (pseudohypoparathyroidism)
26
Q

What are some causes of tertiary hyperparathyroidism?

A
  • Prlonged secondary hyperparathyroidism causing unregulated secretion of PTH
  • Kidney transplant
27
Q

What are some causes of hypoparathyroidism?

A
  • Postsurgical (most common)
  • Postradiation
  • Autoimmune
  • Iron deposition in people with thalassaemia
  • Hypo/hypermagnasaemia
  • pseudohypoparathyroidism
  • DiGeorge syndrome
28
Q

What is DiGeorge Syndrome and some symptoms?

A

Absence of PTH glands

Sx:
- Heart defects
- Cleft palate
- Thymus aplasia

29
Q

If PTH is low and calcium is high what is this indicative of?

A

PTH attempting to correct hypercalcaemia
- MALIGNANCY
- Sarcoidosis
- Thyrotoxicosis
- Milk Alkali Syndrome

30
Q

What is sarcoidosis?

A

Ectopic 1α hydroxylase enzyme production from macrophages

31
Q

What is the commonest cause of hypercalcaemia?

A
  • Primary hyperparathyroidism (in community)
  • Malignancy (in hospital)
32
Q

What are some symptoms of hypercalcaemia?

A
  • Moans (abdo pain, constipation, N+V, decreased appetite, peptic ulcer disease)
  • Groans (Confusion, dementia, depression)
  • Stones (renal)
  • Bones (pain)
  • Thrones (polyuria)
  • Muscle weakness
33
Q

What are three hypercalcaemic malignancies?

A
  1. PTH-like peptide releasing tumours (PTHrp) = small cell lung cancer
  2. Bone metastases
  3. Haematological malignancy (cytokine release destroys bone)
34
Q

What is the treatment of hypercalcaemia?

A

Treat cause
- Fluids (IV 0.9% NaCl)
- Bisphosphonates (if malignancy)

35
Q

What are some complications of hypercalcaemia?

A
  • Renal stones
  • Pancreatitis
  • Peptic ulcer disease
  • Band keratopathy
  • Bone changes: pepperpot skull (lytic lesions), osteitis fibrosa cystica
36
Q

What are causes of hypercalcaemia with hyperalbuminaemia?

A

Increased Urea:
- Dehydration

Normal Urea:
- Cuffed specimen

37
Q

What are causes of hypercalcaemia with normal albumin/hypoalbuminaemia?

A

Hypophosphataemia:
- Primary/tertiary hyperparathyroidism

Hyperphosphataemia:
High ALP:
- Bone metastasis
- Thyrotoxicosis
- Sarcoidosis

Normal ALP:
- Myeloma
- Excess Vit D
- Sarcoid
- Milk Alkali Syndrome

38
Q

What are some symptoms of hypocalcaemia?

A

CATs go numb:
- C: Convulsions
- A: Arrhythmias (e.g. prolonged QT)
- T: Tetany
- Parasthesias (hand, mouth, feet, lips)

  • Neuromuscular excitability: Trousseau’s + Chvostek’s signs (hyperreflexia, laryngeal spasm convulsions)
39
Q

What is the treatment of hypocalcaemia?

A

IF symptomatic OR Ca<1.875:
- Parenteral calcium (IV 10% calcium gluconate)

Asymptomatic/mild:
- Oral calcium supplementation
- IF low PTH/Vit D: Vit D supplements (active form)

40
Q

What are some causes of hypocalcaemia?

A
  • Artefact

Hyperphosphataemia:
- CKD
- Hypoparathyroidism
- Pseudohypoparathyroidism
- Hypomagnesaemia

Normal/Hypophosphataemia:
- Osteomalacia
- Acute pancreatitis
- Overhydration
- Respiratory alkalosis

41
Q

What are some RFs for Renal Stones (nephrolithiasis)?

A
  • Dehydration
  • Abnormal Urine pH (meat intake, renal tubular acidosis)
  • Increased excretion of stone constituents
  • Urine infection
  • Anatomical abnormalities
42
Q

What is the preventative management of renal stones?

A
  • Avoid dehydration
  • Reduce oxalate intake
  • Maintain normal Ca intake
  • Thiazides = hypocalciuric
  • Cirtate (alkalinise urine)
43
Q

What is struvite comprised of?

A

Magnesium + Ammonium phosphate

44
Q

What are the different types of renal stones and their XR appearance?

A
  • Calcium = radio-opaque
  • Calcium oxalate = radio-opaque
  • Calcium phosphate = radio-opaque
  • Triple phosphate (Struvite) = radio-opaque (stag-horn)
  • Uric acid = radiolucent
  • Cysteine = Radio-opaque (light)
  • Xanthines = Lucent
45
Q

What is the first-line investigation for renal stones?

A

CTKUB without contrast (<24hrs of presentation)

  • USS: pregnant women, children, young people
46
Q

What is the management for renal stones?

A

IM diclofenac (analgesia)

  • <=5mm diameter = conservative
  • 6-20mm: Lithotripsy/uteroscopy
  • > 20mm: Percutaneous nephrolithotomy
47
Q

What are some investigations for recurrent renal stones?

A
  • Bloods
  • Stone analysis
  • Spot urine
  • 24hr urine

Pathology (Guide) (84 decks)

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