Thyroid Gland

Question 1

Describe the structure of the thyroid gland

Answer 1

• bi-lobed structure either side of trachea
• highly vascular (blood vessels)

Question 2

What hormones are associated with the thyroid gland?

Answer 2

• thyroid hormones
• calcitonin
• parathyroid hormone

Question 3

What are the 2 thyroid hormones?

Answer 3

• thyroxine (T4)
• tri-iodothyronine (T3)

Question 4

What cells produce the thyroid hormones?

Answer 4

follicular cells

Question 5

What cell produces calcitonin?

Answer 5

C-cells

Question 6

What produces parathyroid hormone?

Answer 6

Parathyroid gland
- within & adjacent to thyroid gland

Question 7

What is the functional unit of the thyroid gland?

Answer 7

follicle

Question 8

Describe the cellular structure of the thyroid gland (and draw)

Answer 8

Hollow balls of cuboidal cells linked by tight junctions.
(- follicle cavities surrounded by follicle cells in circular shape)

Question 9

What do follicle cavities contains?

Answer 9

protein colloid
- esp thyroglobulin

Question 10

What exchanges occur through the follicle cell?

Answer 10

all exchanges between colloid & blood (mainly amino acid tyrosine and iodine)

Question 11

What is the 1st step of thyroid hormone synthesis?

Answer 11

active transport of I- from blood into follicle cell

Question 12

What is the 2nd step of thyroid hormone synthesis?

Answer 12

• synthesis of thyroglobulin
• secrete into colloid in the follicle cavity

Question 13

What is the 3rd step of thyroid hormone synthesis?

Answer 13

• oxidation of I- by thyroid peroxidase
• iodination of thyroglobulin

Question 14

What is the 4th step of thyroid hormone synthesis?

Answer 14

coupling of iodinated tyrosine residues to make T4 and T3

Question 15

What is the 5th step of thyroid hormone synthesis?

Answer 15

uptake of luminal colloid into follicle cell

Question 16

What is the 6th step of thyroid hormone synthesis?

Answer 16

release of thyroid hormones by lysosomal digestion

Question 17

What is the 7th step of thyroid hormone synthesis?

Answer 17

secretion of T4 and T3 into bloodstream

Question 18

What are the actions of the thyroid hormones?

Answer 18

1. increase BMR + heat production
2. increase rate + force of contraction in heart
3. promote normal growth + development
4. stimulate red blood cell production

Question 19

What is hypothyroidism?

Answer 19

thyroid hormone deficiency

Question 20

What are the causes of hypothyroidism?

Answer 20

• iodine deficiency
• congenital hypothyroidism
• Hashimoto’s disease

Question 21

What are the effects of hypothyroidism?

Answer 21

• weight gain
• lethargy & muscle weakness
• reduced heart rate & cardiac output
• decreased gut motility & constipation
• decreased sweating & dry skin
• possible goitre
• cretinism (if left untreated)

Question 22

What is Hyperthyroidism?

Answer 22

thyroid hormone excess

Question 23

What causes hyperthyroidism?

Answer 23

• Grave’s disease
• tumours of pituitary/thyroid glands

Question 24

What are the effects of hyperthyroidism?

Answer 24

• weight loss
• hyperactivity, anxiety, irritability
• tachycardia and/or fibrillation
• increased cardiac output & blood pressure
• increased gut motility
• excess sweating & heat production
• possible goitre
• protruding eyes

Question 25

What is a goitre?

Answer 25

Swelling of thyroid gland