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PHA223 > Thyroid and parathyroid gland > Flashcards

Thyroid and parathyroid gland Flashcards

1
Q

Where is the thyroid gland located?

A

below the layrnx and anterior (front) to the trachea

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2
Q

name the 2 parathyroid glands

A

superior parathyroid gland

inferior parathyroid gland

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3
Q

What is the thyroid gland made up of?

A

colloids

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4
Q

What type of cells line colloid cells?

A

follicular cells

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5
Q

What do follicular cells do?

A

trap iodine

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6
Q

What are between follicular cells of colloids?

A

parafollicular cells (C cells)

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7
Q

What do parafollicular cells secrete?

A

calcitonin (peptide hormone)

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8
Q

What does calcitonin do?

A

decreases plasma calcium concentrations (has parathyroid hormone effects)

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9
Q

What connects the 2 loops of the thyroid gland?

A

the isthmus

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10
Q

What is the thyroid gland responsible for?

A

regulation of thryoid hormone secretion

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11
Q

What is the synthesis and regulation of thryoid hormones regualted by?

A

TSH and TRH

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12
Q

TRH

A

thyrotropin releasing hormone

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13
Q

What 2 hormones does the thyroid gland secrete?

A

T4 and T3

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14
Q

% of T4 and T3 that are secreted

A

90% T4

10% T3

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15
Q

What does T4 stand for?

A

thyroxine

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16
Q

What does T3 stand for?

A

tri iodo thyronine

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17
Q

T3 and T4 in circulation

A

bound to thyroxine-binding globulin (TBG), thyroxine-binding prealbumin or albumin

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18
Q

Are bound thyroid hormones active or inactive?

A

inactive

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19
Q

What do thyroid hormones affect?

A

growth and maturation of tissues
cell metabolism
heat production
oxygen consumption

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20
Q

Where are the parathyroid glands located?

A

behind the upper and lower poles of the thyroid gland

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21
Q

What do the parathyroid glands produce?

A

parathyrid hormone

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22
Q

What does parathyroid hormone do?

A

regulator of serum calcium

antagonist of calcitonin

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23
Q

What is calcium important for?

A

conduction of electrical impulses in nervous and muscular systems

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24
Q

What is the only element/mineral that has its own regulatory system?

A

calcium

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25
Q

What regulates calcium in the body?

A

parathyroid gland

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26
Q

What happens when there is a decrease in serum calcium?

A

increased PTH (parathyroid hormone) secretion

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27
Q

What does PTH do in the body?

A

acts on bone, kidney, gut to icnrease serum calcium levels

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28
Q

normal range of plasma calcium

A

9-10 mg/dl

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29
Q

normal calcium levels in the body in mmol/L

A

2.25 mmol/L

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30
Q

What can alterations of parathyroid function cause?

A

hyperparathyroidism and hypoparathyroidism

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31
Q

What is primary hyperparathyroidism?

A

excess secretion of PTH from one or more parathyroid glands

32
Q

What happens if there is an imbalance in calcium homeostasis of the blood?

A

high Ca levels:
- thyroid gland releses calcitonin
- calcitonin stimulates calcium salt to deposit in bone
- Ca levels fall
low Ca levels:
- parathyroid glands release parathyroid hormone (PTH)
- osteoclasts degrade bone matrix and release Ca into blood
- raises Ca levels

33
Q

What is secondary hyperparathyroidism?

A

increase in PTH secondary to a chronic disease

34
Q

What is hypoparathyroidism and what causes it?

A

abnormaly low PTH levels

usually caused by parathyroid damage in thyroid surgery

35
Q

What usually causes hyperparathyroidism?

A

due to a benign growth of 1:4 parathyroid glands

36
Q

What does hyperparathyroisidm cause?

A

induces abnormally high cerum Ca levels
bone decalcification
development of kidney stones

37
Q

signs of hyperparathyroidism?

A 
fatigue
apathy (lack of interest/enthusaism)
muscle weakness
vomiting
hypertension
demineralisation of bones
development of kidney stones
38
Q

When does hypercalcemic crisis occur?

A

when Ca levels are over 15 mg/dl (3.75 mmol/L)

39
Q

What sympoms does hypercalcemic crisis cause?

A

neurological
cardiovascular
renal symptoms

40
Q

What treatment is used for hypercalcemic crisis?

A

treatment to decrease serum calcium

  • IV fluids (saline 0.9% 2-4L/day)
  • phosphate therpay (IV)
  • calcitonin (inc excretion of Ca)
  • dialysis (if the others don’t work after 48hrs)
41
Q

What causes hypothyroidism?

A

accidental removal of parathyroid glands during thyroid surgery

42
Q

What are hypoparathyroidism symptoms casued by?

A

hypocalcemia and hyperphosphatemia

43
Q

Symptoms of hypoparathyroidism

A

neuromuscular irritability
tetany
- numbness, tingling, cramps
- bronchospasm, laryngeal spasm, carpopedal spasm

44
Q

What is carpopedal spasm?

A

involuntary contraction of the feet/hands

45
Q

management of hypoparathyroidism

A

calcium gluconate

10-20ml 10% IV over 10-20 mins

46
Q

What transporters take iodide from the blood into the lumen? (2)

A
  1. sodium iodide symporter (NIS)

2. pendrin 1 (PDS) (iodide chloride transporter)

47
Q

What is the oxygenation of iodide and its incorporatin into the thyroid globulin called?

A

organification of iodide

48
Q

What enzyme catalyses the oxidation of iodide?

A

thyroperoxidase

49
Q

What enzyme catalyses the oxidation of iodide?

A

thyroperoxidase

50
Q

What enzyme catalyses the oxidation of iodide?

A

thyroperoxidase

51
Q

What do tyrosine residues form in the thyroid globulin?

A

MIT - monoidothyrosine (position 3 on the ring)

DIT - diidothyroisine (at position 5)

52
Q

3 main steps in thyroid hormone synthesis

A
  1. uptake of thyroid hormone into cells
  2. oxidation of iodide, iodination/organification and coupling
  3. endocytosis and seretion of thyroid hormones
53
Q

3 main steps in thyroid hormone synthesis

A
  1. uptake of thyroid hormone into cells
  2. oxidation of iodide - iodination and coupling
  3. endocytosis and seretion of thyroid hormones (T3 &4)
54
Q

3 main steps in thyroid hormone synthesis

A
  1. uptake of thyroid hormone into cells
  2. oxidation of iodide - iodination and coupling
  3. endocytosis and seretion of thyroid hormones (T3 &4)
55
Q

3 main steps in thyroid hormone synthesis

A
  1. uptake of thyroid hormone into cells
  2. oxidation of iodide - iodination and coupling
  3. endocytosis and seretion of thyroid hormones (T3 &4)
56
Q

3 major thryoid-binding proteins

A

TBG - thyroid binding globulin
TBPA - thyroxine binding prealbulin
albumin

57
Q

What 2 molecules form to make T3?

A

MIT and DIT

58
Q

What molecules form to make T4?

A

2 DIT molecules

59
Q

How much T4 and T3 does TBG (thyroid hormone-binding globulin) carry?

A

70% of T4 and T3

60
Q

How much T3 and T4 does TBPA carry?

A

10% of circulating T4 and less amounts of T3

61
Q

How much T3 and T4 does albumin carry?

A

15% of circulating T3 and T4

62
Q

Is T3 or T4 more active?

A

T3

63
Q

How is T4 converted to T3?

A

an iodine is removed from the outer ring of T4 to give T3

64
Q

What removes and iodine from T4 to give T3?

A

5/3 deiodinase

65
Q

What is rT3?

A

reverse T3

-> inactive

66
Q

What does 5’/3’ deiodinases do?

A

removes an iodine from the inner ring of T4 to give reverse T3 (rT3)

67
Q

Where is TRH synthesised and released from?

A

hypothalamus

68
Q

What secretes TSH?

A

anterior pituitary

69
Q

What stimulates the secretion of TSH from the anterior pituitary?

A

hypothalamic TRH

70
Q

What causes inhibition of TRH?

A

when there’s high levels of circulating thyroid hormone (T3 and T4)

71
Q

What substances suppress TSH secretion?

A

dopamine
somatostatin
glucocorticoids

72
Q

What are T3 and T4 bound to in the plasma?

A

thyroxine-binding globulin

73
Q

How do T3 and T4 dissociate from thyroxine-binding plasma proteins?

A

diffusion or active transport

74
Q

What happens to T4 when it enters the cell?

A

it is enzymatically deiodinated to T3 which enters the nucleus and attaches to specific receptors

75
Q

What happens when T3 attaches to specific receptors in the nucleus?

A

the receptors are activated and it promotes the formation of RNA and protein synthesis
this is responsible for the effects of T4

76
Q

functions of thryoid hormones

A
  • increases metabolism and protein synthesis

- influences growth and development in children (mental development and sexual maturity)

77
Q

How is thyroid hormone secretion regulated?

A

hypothalamus releases TRH
causes the anterior pituitary to release TSH
causes the thyroid gland to release T3 and T4
- this increases metabolism rate/heat production
- enhances growth/CNS development
- enhances sympathetic activity

PHA223 (43 decks)

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