The Thyroid Gland

Question 1

What are the two general functions of the thyroid?

Answer 1

Development and metabolism

Question 2

What is the structure of the thyroid gland?

Answer 2

Follicular cells surround spheres of colloid

Question 3

What do follicular cells synthesise and secrete?

Answer 3

Thyroid Hormone

Question 4

What do C-cells secrete?

Answer 4

Calcitonin

Question 5

What are the two forms of TH?

Answer 5

T4 and T3

Question 6

What is the major form of TH?

Answer 6

T4

Question 7

Which form of TH is more active?

Answer 7

T3

Question 8

Where is T3 converted?

Answer 8

Target cells

Question 9

What are the types of plasma protein that is bound to TH?

Answer 9

Thyroid binding globulin (mainly), transthyretin and albumin

Question 10

What type of receptors are the TH receptors?

Answer 10

Nuclear

Question 11

What does Thyroid hormone receptor activation require?

Answer 11

Dimerisation with another TR or retinoid X receptor

Question 12

What are the two genes that encode thyroid hormone receptors?

Answer 12

TR alpha and beta

Question 13

What are the subtypes of TRs?

Answer 13

1 and 2 of each

Question 14

Which TR subtype is nonfunctional?

Answer 14

TRalpha2

Question 15

What are the three main domains in a thyroid hormone receptor?

Answer 15

• where coregulatory factors bind
• DNA binding domain in the middle
• hormone recognition element

Question 16

Why is selenium essential in the diet?

Answer 16

3-iodothyronine selenodeiodinases D1-3 control the amount of active T3 receptors there are

Question 17

Which of the 3-iodothyronine selenodeiodinases increase T3 levels and which decrease?

Answer 17

D2 increases and D3 decreases

Question 18

Do thyroid hormones need transporters to move across the cell membrane?

Answer 18

Yes

Question 19

What is the cause and symptoms of Allen-Herndon-Dudley syndrome?

Answer 19

Mutations in MCT8 transporters of TH

Associated with psychomotor retardation

Question 20

How does TH increase metabolic rate?

Answer 20

Increase number and size of mitochondria, positive ionotropic and chromotropic effects on heart and synergies with sympathetic nervous system

Question 21

What energy metabolism functions does TH partake in?

Answer 21

Partially antagonises insulin signalling, gluconeogenesis and lipolysis

Question 22

What type of feedback underlies TH production?

Answer 22

Negative

Question 23

What do hypothalamic neurosecretory cells release?

Answer 23

Thyrotrophin releasing hormone into the portal capillaries

Question 24

What does TRH stimulate?

Answer 24

Thyrotrophs or anterior pituitary to secrete thyroid stimulating hormone

Question 25

What type of receptor is the receptor for TSH?

Answer 25

GPCR

Question 26

What is the main effect of TSH?

Answer 26

Adenylate cyclase -> cAMP and PRA release, causing iodide uptake and the transcription of key enzymes

Question 27

What does TSH cause?

Answer 27

- Growth in thyroid gland - increased iodide uptake - stimulates other reactions involved in TH synthesis - stimulates uptake of colloid

Question 28

What are the primary and secondary problems in hyperthyroidism?

Answer 28

``` Primary = thyroid gland Secondary = pituitary region ```

Question 29

What is Graves’ disease?

Answer 29

Primary hyperthyroidism

Question 30

How does Graves’ disease occur?

Answer 30

Autoimmune

Question 31

What are the symptoms of Graves’ disease?

Answer 31

Weight loss, tachycardia, fatigue, diffuse goitre and opthamopathy

Question 32

What are the pharmacological signs of Graves’ disease?

Answer 32

High circulating TH, low TSH

Question 33

What is hashimotos?

Answer 33

Primary hyperthyroidism

Question 34

What causes hashimotos?

Answer 34

Autoimmune

Question 35

What are the pharmacological effects of hashimotos?

Answer 35

Low circulating TH, high TSH

Question 36

What are the symptoms of hashimotos?

Answer 36

Lethargy, intolerance to cold, lack of growth and development and diffuse goitre