Thyroid Function in Health and Disease Flashcards Preview

MD1 Endocrine > Thyroid Function in Health and Disease > Flashcards

Flashcards in Thyroid Function in Health and Disease Deck (59)
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1

What are the functions of the thyroid gland?

Secrete thyroid hormones > regulate metabolism
Secrete calcitonin > regulate Ca levels

2

What is the structure of the thyroid gland?

2 lobes joined by isthmus

3

What is the location of the thyroid gland?

Below larynx
Above trachea
Anterior in neck

4

What cells surround the colloid?

Follicular cells/thyrocytes

5

Where is thyroglobulin located?

In colloid

6

Where are the C cells?

In interstitial spaces

7

What is the function of C cells?

Secrete calcitonin

8

How are thyroid hormones synthesised?

1. Follicular cell synthesises enzymes and thyroglobulin for colloid
2. Na/I symporter brings iodide into cell > pendrin transporter moves iodide into colloid
3. Enzymes add iodine to tyrosine > make T3 and T4
4. Thyroglobulin taken back into cell in vesicles
5. Intracellular enzymes separate T3 and T4 from protein
6. Free T3 and T4 enter circulation

9

What is the role of thyroglobulin?

Stops iodine from diffusing out

10

Where do we get our iodine from?

Diet

11

What are the uses of iodine in the body?

Thyroid hormone synthesis

12

What are the structural components of thyroid hormone?

Iodine
Tyrosine derivative

13

What are the proportions of T3 and T4 made by the thyroid gland?

T3 = 10%
T4 = 90%

14

How much T3 is derived from T4?

80%

15

Why are thyroid hormones bound to plasma proteins?

Because lipophilic

16

Where is thyroid stimulating hormone (TSH) released from?

Anterior pituitary

17

What does TSH do?

Stimulates all steps in thyroid hormone synthesis

18

Where is thyroid releasing hormone (TRH) released from?

Hypothalamus

19

What increases levels of TRH secretion?

Cold in infants only known factor

20

What decreases levels of TRH secretion?

Stress

21

What is the half-life of T4?

6-7 days

22

What is the half-life of T3?

1 day

23

What are the factors affecting release of thyroid hormones?

Tonic release

24

What are the target tissues of thyroid hormones?

Most cells of body

25

What are the actions of thyroid hormones?

Increase basal metabolic rate and oxygen consumption
Modulate metabolism
Sympathomimetic effect
- Increases HR
- Increases CO

26

Is thyroid hormone essential for life?

No, but essential for child growth and development

27

How does thyroid hormone promote growth?

Foetal life
After birth, essential for GH and IGFs actions

28

When is thyroid hormone needed for nervous system development?

Before and after birth

29

When does goitre occur?

In both hypothyroidism and hyperthyroidism

30

What is primary hypothyroidism?

Thyroid failure
Decreased T3 and T4
Increased TSH