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ER Week 1 > Parathyroid Pathology > Flashcards

Parathyroid Pathology Flashcards

1
Q

The parathyroid glands are derived from what embryological structures?

A

upper pair from fourth pharyngeal pouch

lower pair from third pharyngeal pouch

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2
Q

What organ do the parathyroid glands descend with?

A

the thymus

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3
Q

Unrelated, but what happens to the first pharyngeal groove and pouch?

A

forms inner ear

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4
Q

What happens to the 2nd pharyngeal pouch?

A

it gets obliterated by the tonsils

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5
Q

What happens to the 5th pharyngeal pouch?

A

the ultimoibranchial body

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6
Q

What are the two types of cells in the parathyroid gland?

A

the chief cells and the oxyphil cells

the water clear cells?

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7
Q

What are the 5 main actions of PTH?

A
  1. increased bone resorption
  2. increased renal reabsorption of calcium
  3. increased renal excretion of phosphate
  4. increased renal conversion of vitamin D to its active form
  5. Increased gut absorption of calcium
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8
Q

All of these actions serve to do what?

A

increase serum calcium

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9
Q

So why does PTH activate vitamin D?

A
  1. it stimulats gut to absorb more calcium
  2. it helps PTH get the calcium out of bone
  3. It stimulates the kidneys to reabsorb calcium
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10
Q

What enzyme in the liver converts vitamin to 25 (OH)D?

A

25 hyroxylase

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11
Q

What enzyme in the kidney converts 25(OH)D into active 1,25(OH)2D?

A

alpha-1 hydroxylase

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12
Q

What controls PTH release?

A

free calcium

low serum calcium triggers PTH synthesis and release

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13
Q

So what will hyperparathyroidism cause?

A

hypercalcemia

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14
Q

What are 4 other common causes of hypercalcemia?

A
  1. malignancy = metastases or PTH-related protein
  2. vitamin D overdose
  3. Thiazide diuretics (reduce excretion)
  4. Milk-alkali syndrome
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15
Q

What is the MD PIMPS ME mnemonic for hypercalcemia?

A

Malignancy
Diuretics

Parathyroidism
Idiopathic
Megadose of vitamin D
Paget disease
Sarcoidosis

Milk-alkali syndrome
Endocrine (thyrtoxicosis)

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16
Q

What is the most common cause of SYMPTOMATIC hypercalcemia?

A

malignancy

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17
Q

What is the most common cause of ASYMPTOMATIC hypercalcemia?

A

hyperparathyroidism

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18
Q

Wht is primary hyperparathyroidism a problem of?

A

the parathyroid gland itself (usually an adenoma)

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19
Q

What is secondary hyperparathyroidism? What’s the usual cause?

A

chronic hypocalcemia, leading to hyperparathyroidism

usually from renal failure

20
Q

What is tertiary hyperparathyoridism?

A

when there are autonmous parathyroids that don’t listen to other signals

21
Q

What is pseudohyperparathyroidism from?

A

PTH-related protein being secreted by a lung cancer

22
Q

What are the three causes of primary hyperparathyroidism?

A

parathyroid adenoma
parathyroid hyperplasia
parathyroid carcinoma

23
Q

As far as epidemiology goes, is primary hyperparathyroidism rare or common?

A

common - nearly 2.5 cases per 1000 adults

24
Q

Primary hyperparathyroidism is usually asymptomatic. What are the signs and symptoms when it’s not?

A

stone: kidney stones
bone: bone pain, brown tumors
groan: GI problems
moan: mental changes

25
Q

What will the lab findings be in primary hyperparathyroidism?

A

increased serum PTH
increased serum Ca
decreased serum phosphate

26
Q

What are the changes that occur in bones with primary hyperparathyroidism?

A
  1. osteoclast activation (so bone resorption)
  2. osteoblast activation
  3. brown tumors
  4. osteitis fibrosa cystica
27
Q

What is the signalling pathway that turns on osteoclasts?

A
  1. RANK ligand on the ostoblast binds the RANK receptor on the ostoclast precursor which activates the osteoclast
28
Q

What is the other pathway?

A

M-CSF ligand on the osteoblast binds to the M-CSF receptor on the osteoclast precursor which activates the osteoclast

29
Q

What will bone look like when there’s high osteoclastic activity?

A

the surface will look eroded

30
Q

Describe a brown tumor.

A

The high osteoclast activity chews away at bone, which leads to microfractures and hemorrhage with blood cells coming into clean up the damage. the blood just pools there and turns brown, hence the name

looks like a tumor on imaging, but it’s not really a tumor

31
Q

What does osteitis fibrosa cystica look like/

A

When the hyperparathyroidism is long standing, you can start to see punched-out lesions in the skull and between the teeth

32
Q

What is the commonest cause of primary hyperparathyroidism?

A

parathyroid adenoma

33
Q

True or false: Parathyroid adenomas are usually solitary.

34
Q

Some parathyroid adenomas have genetic defects. What are two common ones?

A
  1. PRAD 1 overexpression

2. MEN 1 loss or mutation

35
Q

What does a parathyroid adenoma look like microscopically?

A

It typically looks like normal parathyroid but there are a few hints

an adenoma will usually have a fibrous capsule (which will NOT be invaded by malignajnt cells) and will be devoid of fat

36
Q

True or false: parathyroid hyperplasia usually only affects one of the parathyroid glands.

A

false - usually all four

37
Q

Parathyroid carcinoma is a super rare cause of primary hyperparathyroidism. What is the main symptom for parathyroid carcinoma?

A

abrupt onset of bone pain

38
Q

Parathyroid carcinoma is usually well-differentiated. So what?

A

This is a problem, because it means that it looks a lot like a benign parathyroid adenoma! It can be really hard to tell them apart

39
Q

What is the 5 y survival for parathyroid carcinoma?

40
Q

What will parathyroid carcinoma look like microscopically?

A

It will look just like an adenoma, except there will be cells invading into the surrounding capsule

41
Q

Renal failure is the most common cause of secondary hyperparathyroidism (chronic hypocalcemia), but what are two others?

A
  1. diet poor in calcium

2. vitamin D deficiency

42
Q

Describe the pathophysiology of why renal failure causes secondary hyperparathyroidism?

A
  1. the kidneys can’t ecxcrete phosphate
  2. serum phosphate goes up
  3. this makes serum calcium go down
  4. the hypocalcemia stimulates the parathyroids
43
Q

What are the three (four) main causes of hypoparathyroidism?

A
  1. iatrogenic
  2. Hereditary: DIGeorge syndrome and agenesis (x-linked)
  3. idiopathic atrophy
44
Q

What ais the main cause of iatrogenic hypoparathyoridism?

A

When they need to surgically remove the thyroid gland and take the parathyroids along with it.

45
Q

What are the signs ans symptoms of hypoparathyroidism?

A

neuromuscular irritabiliby (due to the hypocalcemia) with perioral numbness, muscle weakness, cramps, tetany, Chvostek’s sign, Trousseau’s sign

heart arrhythmias

dental abnormalities

46
Q

What is Chvostek’s sign?

A

stroke the cheek and it will twitch

47
Q

What is Trousseau’s sign?

A

slowly inflate a BP cuff on someone’s arm and it will cramp up

ER Week 1 (11 decks)

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