The Thyroid Gland

Question 1

What are the 2 active forms of thyroid hormone?

Answer 1

T3 triiodothyronine

T4 thyroxine

Question 2

At what vertebral level does the thyroid gland sit at?

Answer 2

C5-T1

Question 3

What 2 cells are found in the thyroid gland?

Answer 3

C (clear) cells

Follicular cells

Question 4

What is the function of C cells?

Answer 4

Secrete calcitonin

Question 5

What is the function of follicular cells?

Answer 5

Support thyroid hormone synthesis and surround hollow follicles
Manufacture thyroglobulin
Actively concentrate iodide

Question 6

What is found in the centre of thyroid follicles?

Answer 6

Colloid

Question 7

How is iodide transported into colloid?

Answer 7

Pendrin transporter

Question 8

What inhibits iodide transport into thyroid gland?

Answer 8

Thiocyanates

Question 9

Where is thyroid peroxidase found?

Answer 9

Colloidal side of cells

Question 10

What is the role of thyroid peroxidase?

Answer 10

Catalyses the addition of iodide to tyrosine residues in thyroglobulin

Question 11

What is made from the addition of one iodide to tyrosine?

Answer 11

MIT (monoiodotyrosine)

Question 12

What is made from the addition of 2 iodide to tyrosine?

Answer 12

DIT (diiodotyrosine)

Question 13

What is made from MIT+DIT?

Answer 13

T3

Question 14

What is made from DIT+DIT?

Answer 14

T4

Question 15

What plasma protein does T3 and T4 bind to?

Answer 15

Thyroxine-binding globulin

Question 16

What is the typical half life for T3?

Answer 16

1 day

Question 17

What is the typical half life for T4?

Answer 17

6 days

Question 18

What deiodinates T4?

Answer 18

Deiododinase enzymes

Question 19

What are the main functions of thyroid hormone?

Answer 19

Raises metabolic rate and promotes thermogenesis 
Increase hepatic gluconeogenesis 
Net increase in proteolysis 
Net increase in lipolysis 
Foetal brain development 
Critical for growth

Question 20

What are the causes of hyperthyroidism?

Answer 20

Graves disease

Thyroid adenoma

Question 21

What are the symptoms of hyperthyroidism?

Answer 21

Weight loss 
Heat intolerance 
Muscle weakness 
Increased HR 
Hyperexcitable reflexes

Question 22

What are the causes of hypothyroidism?

Answer 22

Hashimoto’s disease
Idiopathic
Dietary iodine deficiency

Question 23

What are the symptoms of hypothyroidism?

Answer 23

Weight gain 
Cold intolerance 
Slow speech 
Slow reflexes 
Fatigue 
Slow HR 
Weaker pulse

Question 24

What is the term used for a thyroid gland enlargement?

Answer 24

Goitre

Question 25

What can cause goitre formation?

Answer 25

Increased trophic action of TSH on thyroid follicular cells

Over activity as a result of autoimmune disease