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Endocrinology > Parathyroid > Flashcards

Parathyroid Flashcards

1
Q

How many parathyroid glands are there?

A

4

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2
Q

Where are they located in relation to the thyroid gland?

A

Posterior aspect of the thyroid gland

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3
Q

Which cells secrete parathyroid hormone?

A

Chief cells

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4
Q

What kind of hormone is parathyroid hormone?

A

A polypeptide

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5
Q

What is the primary stimulus for parathyroid hormone?

A

Hypocalcaemia

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6
Q

What is the primary inhibitor of parathyroid hormone?

A

Hypercalcaemia

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7
Q

What is another name for a parafollicular cell?

A

C-cells

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8
Q

What are parafollicular cells stimulated by?

A

Hypercalcaemia

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9
Q

What are parafollicular cells inhibited by?

A

Hypocalcaemia

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10
Q

Where is calcitonin produced from?

A

Parafollicular cells (or C -cells)

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11
Q

What do parafollicular cells produce?

A

Calcitonin

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12
Q

What stimulates calcitonin release?

A

Hypercalcaemia

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13
Q

What stimulates parathyroid release?

A

Hypocalcaemia

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14
Q

What is a humoral stimulus?

A

Endocrine function which is controlled by change in electrolytes i.e. hypocalcaemia leading to increased parathyroid release

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15
Q

What kind of stimulus causes calcitonin or parathyroid release?

A

Humoral stimuli (calcium)

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16
Q

How does PTH effect the bone?

A

Increase osteoclastic activity by activating osteoblasts to release Rank-ligand, which stimulates Rank receptors on osteoclasts

17
Q

What doe osteoclasts do?

A

Resorb bone - releases calcium into the blood

18
Q

What do osteoblasts do?

A

Bone deposition - takes calcium from the blood to build bone

19
Q

What is the significance of Rank Ligand to PTH?

A

Released by osteoblasts in response to PTH causing activation of the osteoclasts

20
Q

What is released by increased osteoclastic activity?

A

Phosphate and calcium

21
Q

How does PTH affect the blood biochemistry?

A

Increases phosphate and calcium release via increased osteoclastic activity, increased calcium uptake by kidney (phosphate is excreted) and increased synthesis of active vitamin D causing increased uptake in the GI tract of calcium

22
Q

How does PTH affect the kidney?

A

DCT to reabsorb calcium by secondary active transport + increases phosphate excretion + increases the expression of 1-alpha-hydroxalase

23
Q

What is the overall effect of PTH?

A

To increase calcium in the blood

24
Q

How is cholecalciferol formed?

A

UV light activates 7-dehydrocholestrol to cholecalciferol

25
Q

What happens to cholecalciferol in the liver

A

Converted to 25-hydroxycholecalciferol via 25-hydroxalase

26
Q

What is the role of 1-alpha-hydroxalase in the kidney?

A

It hydroxalases 25-hydroxycholecalciferol to

1,25-cholecalciferol (calcitriol)

27
Q

What is another name for calcitriol?

A

Vitamin D

28
Q

How is Vitamin D produced?

A

UV light activates 7-dehydrocholesterol which goes to the liver and is converted to 25-hydroxycholecalciferol, which is converted by the kidney to 1,25-cholecalciferol, otherwise known as calcitriol or vitamin D)

29
Q

What is the role of Vitamin D?

A

Increase calcium uptake from the gi tract via calcium channel proteins

30
Q

What kind of hormone is vitamin D?

A

A steroid hormone

31
Q

Which mechanisms cause calcium increase by PTH?

A

Increased GI uptake via vitamin D, Increased osteoclast activity, Increase resorption of calcium in the kidney

32
Q

What is the overall effect of calcitonin?

A

Reduces blood calcium

33
Q

What does calcitonin do in the bone?

A

Directly inhibits osteoclastic activity and thereby increases osteoblastic activity

34
Q

Where do the parathyroid glands develop from in embryological development?

A

Superior glands - pharyngeal pouch 4

Inferior glands - pharyngeal pouch 3

35
Q

What is the blood supply to the parathyroid gland?

A

Inferior and superior thyroid arteries

36
Q

Where is the gene for PTH located?

A

Chromosome 11

37
Q

What is the main cause of primary hyperparathyroidism?

A

A solitary adenoma of the parathyroid gland

38
Q

What is the main cause of secondary hyperparathyroidism?

A

Caused by hypocalcaemia secondary to chronic kidney disease or vitamin D deficiency

39
Q

What is the main cause of tertiary hyperparathyroidism?

A

Prolonged stimulation leads to hyperplasia of the parathyroid gland and insensitivity to calcium levels. This is seen in end stage renal failiure

Endocrinology (16 decks)

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