Brainscape's Knowledge GenomeTM

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


See full index

5. Endocrinology > 5. Thyroid gland and its hormones > Flashcards

5. Thyroid gland and its hormones Flashcards

1
Q

Describe the structure of the thyroid.

A
  1. Follicles
  2. Follicular cells
  3. Parafollicular cells / C cells
  4. Colloid (lumen)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the 3 thyroid hormones?

A
  1. T3 - triiodothyronine
  2. T4 - thyroxine / tetraiodothyronine
  3. Calcitonin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What hormones do the follicular cells / thyrocytes secrete?

A
  1. T3
  2. T4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What hormone is released by the parafollicular cells / C cells?

A

Calcitonin

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

Give 3 functions of thyroid hormones (T3/4).

A
  1. Food metabolism.
  2. Protein synthesis.
  3. Increased sympathetic action e.g. CO and HR.
  4. Heat production.
  5. Needed for growth and development.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which has a longer half life, T3 or T4?

A

T4 - half life of 6-8 days - less active form

T3 - half life of only 1 day - highly active form

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

What is the precursor hormone for the thyroid hormones?

A

Thyroglobulin

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

Where is thyroglobulin (precursor hormone) made in the thyroid?

A

Synthesised in the RER of follicular cells/thyrocytes in the thyroid

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

Describe the process of T3/T4 formation from the precursor hormone, thyroglubulin (TG).

A
  1. TG made in the RER of follicular cells + secreted into the colloid (lumen of the thyroid)
  2. Iodine enters follicular cell from the blood via Na+/I- symporter at the basolateral side (2x Na+ and 1x I-)
  3. Iodine exits the follicular cell into the colloid at the apical side via an ion transporter, pendrin (exchanges 1x Cl- for 1x I-)
  4. Oxidation of iodine via thyroid peroxidase and becomes I2
  5. I2 iodinates tyrosyl residues on TG via thyroid peroxidase to form MIT + DIT
  6. DIT + DIT -> T4 AND MIT + DIT -> T3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the difference between the molecules T3 and T4?

A

MIT + DIT -> T3

DIT + DIT -> T4

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

Which thyroid hormone is the active form, T3 or T4?

A

T3

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

Describe the process of thyroid hormone secretion into the blood.

A
  1. Thyroid hormone stored in colloid on Thyroglobulin (TG)
  2. TSH stimulation from the anterior pituitary
  3. Endocytosis of iodinated TG via vesicle from colloid into follicular cell
  4. Fusing of vesicle + lysosome
  5. Hydrolysis of TG into T3 + T4 via proteases
  6. T3/T4 released via MCT transporter on the basolateral membrane of the follicular cell into the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Do inactive thyroid hormones travel freely or bound to proteins?

A

Bound to proteins:
1. Thyroxine binding globulin or TBG
2. Albumin
3. Transthyretin

Bound T3 and T4 acts like a reservoir of hormone that’s not biologically active.

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

How is T4 converted and activated to T3?

A
  1. In target tissues
  2. Enzyme: 5’-deiodinase
  3. Removes 1 atom of I2
  4. T4 converted to T3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the thyroid axis.

A

Hypothalamus -> TRH -> AP -> TSH -> thyroid -> T3 and T4.

T3/4 have a negative feedback effect on the hypothalamus and the anterior pituitary.

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

What would be the effect on TSH if you had an under-active thyroid?

A

TSH would be raised as you have less T3/4 being produced and so no negative feedback.

17
Q

What would a low TSH tell you about the action of the thyroid?

A

A low TSH indicates an over-active thyroid.

Lots of T4 and T3 is being produced and so there is more negative feedback on the pituitary and less TSH.

18
Q

What is the general effect of the thyroid hormone?

A

↑↑ Na+-K+ ATPase
↑↑ O2 consumption
↑↑ Basal metabolic rate (BMR)

Body temperature

19
Q

What are the effects of the thyroid hormone on the CVS?

A

↑ B1-adrenergic receptors

↑ Ca2+-ATPase

↑ inotropic and chronotropic effects
I.E. ↑ contractility and ↑ HR

↑ cardiac output (CO)

20
Q

What are the catabolic effects of the thyroid hormones?

A

Metabolism of macromolecules:
↑ transport proteins
↑ glucose absorption from GI tract
↑ catecholamine, glucagon, GH activity
↑proteolysis, lipolysis, gluconeogenesis

21
Q

What are the effects of the thyroid hormone on the CNS?

A

Gestational period -> CNS development

Adult period -> ↑ brain activity, ↑ attention span, ↑ memory

22
Q

What are the effects of the thyroid hormone on growth?

A

↑↑ osteoblast + osteoclast activity

↑↑ bone formation and maturation

23
Q

What triggers calcitonin release?

A

High blood calcium levels (above the normal range)

24
Q

How does calcitonin lower blood calcium levels? State 2 ways.

A
  1. In bones
    - Calcitonin binds to receptors on osteoclasts
    - Leads to decreased bone resorption and decreased blood calcium concentration
  2. In kidneys
    - Decreased Calcium + Phosphate reabsorption by principle cells of the DCT
25
Q

What is the normal blood calcium range?

A

8.5 to 10 mg/dl

5. Endocrinology (20 decks)

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