Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BRS - Endo > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

Where is the thyroid gland located?

A

under the larynx or “adams apple”, on top of the trachea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the different parts of the thyroid gland?

A

2 LOBES of the thyroid gland, connected by thyroid connective tissue called ISTHMUS, which is topped with a PYRAMID, which is all under the thyroid cartilage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are the follicles of the thyroid gland lobes arranged?

A

Follicles are units of colloid (a cavity filled w/ sticky fluid) surrounded by follicular cells in a circular arrangement, and further surrounded by parafollicular cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What nerve runs close to the thyroid gland?

A

left recurrent laryngeal nerve (which supplies the vocal cords)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the embryology of the thyroid gland?

A

develops from the floor of the pharynx (base of the tongue), then occurs the development of the thyroglossal duct, divides into 2 lobes + duct disappears leaving the FORAMEN CAECUM, reaching final position in the neck by 7th week.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is the thyroid gland stimulated to produce Thyroid Hormone?

A

stimulated by TSH, released by the anterior pituitary gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does TSH first enter the thyroid gland?

A

TSH in the bloodstream binds to the TSH-R (TSH-receptor) embedded into the follicular cell membranes of the thyroid gland.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What ion is necessary for TH production? How is this ion used?

A

Iodide ions : when TSH binds, Iodide ions are actively transported across the follicular cell membrane to colloid where it’s IODINATED (oxidised).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is Thyroglobulin? Why is it important in TH production?

A

a glycoprotein produced in follicular cells and released into the colloid when TSH binds - it’s combined with the iodide ions in iodination reactions in order to produce TH.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is TPO? Why is it important in TH production?

A

Thyroid Peroxidase gets activated when TSH binds, catalyses the iodination reactions along with H202 (hydrogen peroxide).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What forms when TG combines with Iodide ions?

A

one of two products: MIT (mono-iodo-tyrosine) or DIT (di-iodo-tyrosine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the importance of MIT and DIT in TH production?

A

a coupling reaction between MIT + DIT produces T3, a coupling reaction between 2 DITs produces T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is T3?

A

triiodothyronine, the active form of TH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is T4?

A

thyroxine, the prohormone of TH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What’s the difference between T3 and T4?

A

T4 is the precursor + gets converted into T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Does the thyroid gland produce more T3 or T4?

A

T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is T4 converted into T3?

A

deiodination reaction using the enzyme DEIODINASE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is “reverse T3” and how is it produced?

A

inactive form of T3, created through deiodination of T4 in a different position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What percentage of circulating T3 is due to direct thyroidal secretion?

A

20%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What percentage of circulating T3 is due to deiodination of T4?

A

80%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How are T3 and T4 transported in the blood?

A

mostly by binding to plasma proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What plasma protein are T3 + T4 bound to 70-80% of the time?

A

TBG (thyroid-binding globulin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What plasma protein are T3 + T4 bound to 10-15% of the time?

A

albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What plasma protein are T3 + T4 bound the rest of the time?

A

prealbumin (transthyretin)

25
Q

What is the difference between albumin and prealbumin?

A

prealbumin (transthyretin) is the precursor for albumin

26
Q

How much of T4 and T3 is unbound in the bloodstream?

A

0.05% of T4, 0.5% of T3

27
Q

How does T3 + T4 affect gene expression in target tissues + cells?

A

enters target tissues + cells through receptors, T4 is deiodinated to T3, total T3 enters nucleus and binds THR (thyroid hormone receptor) on the TRE (thyroid responsive element), this alters gene expression by either activating or repressing gene transcription.

28
Q

Why is thyroid hormone important in infants?

A

Essential for fetal growth + development, especially the CNS development

29
Q

What is the lack of thyroid hormone in infants called?

A

Congenital hypothyroidism

30
Q

What can untreated hypothyroidism in infants cause?

A

Cretinism

31
Q

How is congenital hypothyroidism detected in infants?

A

Heel-prick test at birth to detect thyroid hormone levels

32
Q

What is the main function of the thyroid hormone?

A

Stimulates cells to synthesize new proteins

33
Q

How does TH impact growth?

A

Helps w/ growth formation + bone maturation

34
Q

How does TH impact the CNS?

A

Helps w/ maturation of CNS

35
Q

How does TH impact BMS?

A

More increased BMR, more na/k, more ATPase, more oxygen consumption, more heat production.

36
Q

How does TH impact metabolism?

A

Increased glucose absorption, glucogenolysis, gluceneogenesis, lipolysis, protein synthesis + degradation.

37
Q

How does TH impact the cardiovascular system?

A

Increases cardiac output

38
Q

What are the 3 ways in which TH is regulated / controlled?

A

Negative feedback, somatostatin, iodide (Wolff-Chaikoff effect)

39
Q

Are thyroid disorders more common in men or women?

A

Women have a predespesition for autoimmune diseases

40
Q

Which thyroid disorders are more common?

A

All equally common

41
Q

What is primary hypothyroidism?

A

Autoimmune damage to thyroid gland, thyroxine levels decline, TSH levels climb.

42
Q

What is one common form of hypothyroidism?

A

Hashimoto’s thyroiditis

43
Q

What are the symptoms or signs of hypothyroidism?

A
  • Deepening voice
  • Depression and tiredness
  • Cold intolerance
  • Weight gain with reduced appetite
  • Constipation
  • Bradycardia - slower than normal heart rate
  • Eventual myxoedema coma
44
Q

What drug can be used to treat hypothyroidism? How is it administered?

A

Levothyroxine

45
Q

How does levothyroxine work?

A

Provides T4 that can be deiodinated into T3

46
Q

How is dosage worked out for levothyroxine?

A

Blood test, TSH + T4 levels are measured + dosage is worked out accordingly (most common dosage = 100mg)

47
Q

What are some minor side effects of levothyroxine?

A

Weight loss, headache

48
Q

What are some major side effects of levothyroxine?

A

Very rare, increased rapid heart rate, heart attack

49
Q

What other drug can be used to treat hypothyroidism, but isn’t?

A

Liothyronine

50
Q

Why liothyronine not used often?

A

Liothyronine = T3, expensive to produce in comparison to T4, has no benefits as T4 is converted into T3 anyway.

51
Q

Does combination drug therapy of T3 + T4 work?

A

some reported improvement in wellbeing, but complicated by symptoms of ‘toxicity’ – palpitations, tremor, anxiety - often combination treatment suppresses TSH

52
Q

What is primary hyperthyroidism?

A

Thyroid makes too much thyroxine, so thyroxine levels rise and TSH levels drop due to negative feedback.

53
Q

What’s one of the most common forms of hyperthyroidism?

A

Graves’ disease

54
Q

What are some other causes of hyperthyroidism?

A

Toxic multinodular goitre, solitary toxic nodule

55
Q

What is Graves’ disease?

A

Autoimmune disease, Antibodies bind to and stimulate TSH receptor in the thyroid, whole gland smoothly enlarged and whole gland overactive

56
Q

How can Graves disease affect the eyes?

A

Can cause Exophthalmus, the bulging of eyes (usually bilaterally) due to antibodies binding to muscles behind the eyes.

57
Q

How can Graves Disease affect growth of tissue?

A

Can cause Pretibial Myxoedema - antibodies stimulate growth of soft tissue in shins.

58
Q

What are common symptoms of hyperthyroidism?

A 
Heat intolerance
Weight loss with increased appetite
Myopathy
Mood swings
Diarrhoea
Tremor of hands
Palpitations
Sore eyes, goitre

BRS - Endo (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions