Thyroid - normal physiology

Question 1

What is the structure of the thyroid gland?

Answer 1

2 lateral lobes connected by an isthmus

Question 2

What do the thyroid follicles contain?

Answer 2

Colloid

Question 3

What is made in the colloid?

Answer 3

Thyroid hormones

Question 4

What are the follicles lined with?

Answer 4

• Thyroid follicular cells

- C-cells

Question 5

What do thyroid follicular cells make?

Answer 5

Thyroglobulin

Question 6

What do C-cells make?

Answer 6

Calcitonin

Question 7

Give a brief overview of how thyroid hormones are synthesised.

Answer 7

1. TSH stimulates thyroid follicular cells (TFCs) to make thyroglobulin (Tg)
2. Thyroid peroxidase ioninates Tg
3. Lysosomes hydrolyse the ionated Tg and release T3 and T4
4. T3 and T4 are bound to thyroid-binding globulin (TBG) in the blood
5. T4 is deiodinated in the blood to form active T3

Question 8

Does the thyroid release more T3 or T4?

Answer 8

T4 (X10)

Question 9

What are thyroid hormones important for?

Answer 9

• Metabolism (glucose absorption and genesis)
• Oxygen consumption
• Cardiac output
• BP
• Growth
• Brain development
• Sexual maturation

Question 10

Through what receptors do the thyroid hormones act?

Answer 10

Adrenal