CMB1004/L27 Thyroid

Question 1

Give 4 roles of the thyroid in regulation.

Answer 1

Regulating metabolism
Bodyweight
Growth
Development

Question 2

What effect can the thyroid have on the heart?

Answer 2

Increases cardiac output and systolic pressure (HR and stroke volume)

Question 3

What effect can the thyroid have on metabolism?

Answer 3

Increases basal metabolic rate
E.g., glycolysis, oxygen consumption, thermogenesis

Question 4

What effects can the thyroid have on neurology? (2)

Answer 4

Maintains emotional tone/mood
Improves alertness, memory, reflexes and wakefulness

Question 5

What effect does the thyroid have on growth and development?

Answer 5

Essential for foetal neural development and bone growth after birth

Question 6

What is the major product of the thyroid?

Answer 6

Tetraiothyronine
Thyroxine
T4

Question 7

What is the most active product of the thyroid?

Answer 7

Triiodothyronine
T3

Question 8

Which hormone released by the thyroid is involved in calcium homeostasis?

Answer 8

Calcitonin

Question 9

Describe the structure of the thyroid gland. (3)

Answer 9

Two lobes connected by isthmus
Left lobe larger than right
Rich blood supply

Question 10

How many pairs of parathyroid glands are present in humans?

Answer 10

2, 3 or 4

Question 11

What is the functional unit of the thyroid?

Answer 11

Follicles

Question 12

What do follicular cells surround in the thyroid?

Answer 12

Pools of colloid

Question 13

Where are thyroid hormones produced and stored?

Answer 13

Colloid

Question 14

Which cells secrete calcitonin?

Answer 14

C cells

Question 15

Describe the formation of thyroid hormones.

Answer 15

Iodination and coupling of tyrosine

Question 16

Where is thyroglobulin synthesised and released?

Answer 16

Follicular cells
Released into follicular lumen /colloid by exocytosis

Question 17

Where are thyroid hormones synthesised?

Answer 17

Apical follicular membrane-colloid boarder

Question 18

Which enzyme aids iodination of tyrosine within thyroglobulin?

Answer 18

Thyroperoxidase

Question 19

Give 2 precursors to thyroid hormones.

Answer 19

Monoidotyrosine/ T1
Diiodotyrosine/ T2

Question 20

What 2 ions are required for iodination and coupling of tyrosine?

Answer 20

I-
2Na+

Question 21

Which protein allows I- to travel through the thyroid membrane?

Answer 21

Pendrin

Question 22

What is the estimated daily secretion of T4 and T3?

Answer 22

100nmoles T4
5nmoles T3

Question 23

Around what percentage of T4 and T3 are free in the blood?

Answer 23

0.4% T4
0.04% T3

Question 24

What are the 3 major thyroid transporting proteins?

Answer 24

Thyroxine-binding globulin
Thyroxine-binding prealbumin
Albumin

Question 25

Describe the hypothalamic-pituitary-thyroid axis. (3)

Answer 25

Hypothalamus releases thyrotropin-releasing hormone
Anterior pituitary releases thyroid stimulating hormone
Thyroid releases thyroid hormones

Question 26

What effects does TSH have on the thyroid gland? (4)

Answer 26

Increased iodide uptake
Thyroglobulin synthesis
Iodination of thyroglobulin
Pinocytosis of colloid
Lysosomal activity
Size of thyroid cells (cuboidal to columnar)

Question 27

What can deiodination of T4 lead to?

Answer 27

Active or inactive forms of T3

Question 28

Give the enzymes controlling local control of thyroid hormones and which type of T3 they result in. (3)

Answer 28

Type 1 deiodinase - A or I
Type 2 deiodinase - A
Type 3 deiodinase - I (reverse)

Question 29

How do T4 and T3 enter cells?

Answer 29

Through protein channels