Thyroid

Question 1

What is thyroxine derived from?

Answer 1

Tyrosine

Question 2

What type of gland is the thyroid gland?

Answer 2

Ductless

Alveolar

Question 3

How many lobes does the thyroid gland have and how are they connected?

Answer 3

2 lobes connected by the isthmus

Question 4

What is an enlarged thyroid gland called?

Answer 4

Goitre

Question 5

What is the secretory unit of the thyroid gland?

Answer 5

Thyroid follicle

Question 6

What kind of epithelial are found lining the colloid centre?

Answer 6

cuboidal or columnar

Question 7

What protein is found in the colloid?

Answer 7

Thyroglobulin (Tg)

Question 8

Why are the epithelial cells of the thyroid gland polarised?

Answer 8

To allow the movement of things through the cells

Question 9

What does the apical membrane face?

Answer 9

The colloid

Question 10

What does the basolateral membrane face?

Answer 10

the extracellular fluid

Question 11

What do the C cells of the thyroid secrete?

Answer 11

Calcitonin

Question 12

What is the sequence of hormones released to produce thyroid hormone?

Answer 12

TRH -> TSH -> T3 + T4

Question 13

When TSH binds to follicular cells, what does it promote?

Answer 13

iodine uptake
production and released of T3 and T4
promotion of gland growth

Question 14

What are the acute effects of TSH stimulation?

Answer 14

synthesis and secretion of T3 and T4

Question 15

What are the chronic effects of TSH stimulation?

Answer 15

growth and division of follicular cells

enlargement of thyroid gland

Question 16

Which enzyme is required for thyroxine synthesis?

Answer 16

Thyroid peroxidase

Question 17

What kind of molecule is thyroglobulin?

Answer 17

large glycoprotein

Question 18

How is thyroglobulin synthesised?

Answer 18

peptide produced is glycosylated at ER
translocated to Golgi
packaged into secretory vesicles
stored as colloid

Question 19

What are the full names of T3 and T4?

Answer 19

tri-iodothyronine

tetra-iodothyronine

Question 20

Are thyroid hormones fat or water soluble?

Answer 20

Fat soluble

Question 21

Where is Tg iodinated?

Answer 21

At the apical surface

Question 22

Which of T3 or T4 is more potent?

Answer 22

T3 is more potent

Question 23

Which of T3 and T4 has the longer half-life and why?

Answer 23

T4 has a longer half-life

has a greater affinity for TBG

Question 24

What is the full name of TBG?

Answer 24

Thyronine Binding Globulin

Question 25

What effect does oestrogen have on the thyroid?

Answer 25

increased synthesis of TBG | decreased clearance of T3 and T4

Question 26

What happens to T4 in the peripheral tissues?

Answer 26

T4 is converted to T3 by deiodination

Question 27

What is the treatment for hypothyroidism?

Answer 27

T4

Question 28

How do thyroid hormones increase BMR?

Answer 28

increase number and size of mitochondria increase oxygen consumption and heat generation increase nutrient utilisation

Question 29

What effects do thyroid hormones have on the nervous system?

Answer 29

increase myelination increase reflex speed increase mental activity

Question 30

How do the thyroid hormone affect the heart?

Answer 30

They increase cardiac output.

Question 31

What are the features of cretinism?

Answer 31

mental retardation coarse features short stature delayed sexual development

Question 32

What are the signs of hyperthyroidism?

Answer 32

``` heat intolerance increased perspiration weight loss tachycardia increased appetite nervousness or tremors ```

Question 33

Define exopthalmus

Answer 33

Bulging of the eyes that can occur as a result of hyperthyroidism

Question 34

What is main cause of hyperthyroidism?

Answer 34

Grave's disease | Autoimmune production of an antibody that stimulates the TSH receptors.

Question 35

What is the treatment for hyperthyroidism?

Answer 35

Carbimazole

Question 36

How does carbimazole work?

Answer 36

It prevents iodination of the thyroid hormones by inhibiting the enzyme thyroid peroxidase.

Question 37

What are the signs of hypothyroidism?

Answer 37

``` cold intolerance weight gain bradycardia constipation dry skin and brittle nails poor concentration ```

Question 38

What is the main cause of hypothyroidism?

Answer 38

Hashimoto's disease | Autoimmune production of antibodies that block the TSH receptors.

Question 39

How does the thyroid develop in an embryo?

Answer 39

Develops near the tongue and migrates to the base of the neck.

Question 40

When must a heel prick test be done by?

Answer 40

before the baby is 21 days old

Question 41

Where are the T3 receptors?

Answer 41

In the nucleus

Question 42

Name some causes of hypothyroidism other than autoimmune

Answer 42

``` post-surgery radioactive iodine anti-thyroid drugs eg. carbimazole lack of TSH production iodine deficiency ```

Question 43

Name some causes of hyperthyroidism other than autoimmune

Answer 43

excessive T4 therapy excess iodine ectopic thyroid tissue

Question 44

What is the term used to describe normal levels of the thyroid hormones?

Answer 44

Euthyroid

Question 45

What is a hypopit?

Answer 45

When both the TSH and free T4 are low

Question 46

What is the crisis version of hypothyroidism and what are the signs?

Answer 46

Myxoedema coma low temperature unconscious barely responsive to pain

Question 47

What is the crisis version of hyperthyroidism and what are the signs?

Answer 47

Thyroid storm very high temperature high blood pressure deranged

Question 48

The availability of thyroid hormone is tied to the availability of...

Answer 48

iodine