Thyroid

Question 1

What does the follicle consist of?

Answer 1

Cuboid epithelial follicle cells surrounding a colloid-filled lumen

Question 2

What is the purpose of the Thyroid Follicle?

Answer 2

Thyroid hormone synthesis

Question 3

How are iodide ions absorbed into the Thyroid follicle?

Answer 3

Via a Sodium Iodide Transporter (NIS)

Question 4

What type of transporter is an NIS?

Answer 4

Symporter (travels across membrane in same direction as transported molecule)

Question 5

Where in the follicle cell is Tg synthesised?

Answer 5

Rough ER

Question 6

What is Tg?

Answer 6

Thyroglobulin

Question 7

Which molecule mediates the process of Tg Iodination?

Answer 7

Thyroid Peroxidase (TPO)

Question 8

Where is the Iodinated Tg stored?

Answer 8

Colloid

Question 9

Which organelles break down the iodinated Tg?

Answer 9

Lysosomes

Question 10

Which molecules are freed from the proteolysis of iodinated Tg?

Answer 10

T3, T4, MIT, DIT

Question 11

What happens to the MIT and DIT after proteolysis?

Answer 11

They are deiodinated and returned for reuse in the lumen

Question 12

By what process do T3 and T4 enter the bloodstream?

Answer 12

Diffusion

Question 13

Which form is the majority of thyroid hormone transported as?

Answer 13

T4 (roughly 10x more than T3)

Question 14

What are the main characteristic differences between T3 and T4?

Answer 14

T3 is more active, and has a shorter half-life (~1 day); T4 is less active, and has a longer half-life (~5-7 days)

Question 15

What is the primary functional unit of the Thyroid Gland?

Answer 15

Thyroid Follicle

Question 16

Which organ secretes TRH?

Answer 16

Hypothalamus

Question 17

What is TRH?

Answer 17

Thyrotropin-Releasing Hormone

Question 18

Which part of the pituitary gland does TRH stimulate?

Answer 18

Thyrotoph (anterior pituitary gland)

Question 19

Which hormone does the Thyroptroph secrete?

Answer 19

TSH (Thyroid secreting hormone)

Question 20

What effect does TSH have on the Thyroid gland?

Answer 20

Causes cAMP levels to rise, stimulating active transport of Iodide, and synthesis of Tg in rough ER

Question 21

What does TPO do?

Answer 21

Mediates conversion of Iodide to Iodine, and coupling of Iodine to Tyrosine and Thyroglobulin (colloid)

Question 22

What type of Endocrine feedback loop is the Thyroid involved in?

Answer 22

Negative feedback loop

Question 23

What form of Thyroid hormone is used at cellular level?

Answer 23

T3 (more active, and so has higher affinity for Thyroid hormone receptors)

Question 24

How does thyroid hormone affect a cell?

Answer 24

It binds to nuclear receptors TRalpha and TRbeta, forming a hormone receptor complex, which binds to DNA in Thyroid Response Elements region

Question 25

What form of Thyroid hormone is used at cellular level?

Answer 25

T3 (more active, and so has higher affinity for Thyroid hormone receptors)

Question 26

How does thyroid hormone affect a cell?

Answer 26

It binds to nuclear receptors TRalpha and TRbeta, forming a hormone receptor complex, which binds to DNA in Thyroid Response Elements region

Question 27

What form of Thyroid hormone is used at cellular level?

Answer 27

T3 (more active, and so has higher affinity for Thyroid hormone receptors)

Question 28

How does thyroid hormone affect a cell?

Answer 28

It binds to nuclear receptors TRalpha and TRbeta, forming a hormone receptor complex, which binds to DNA in Thyroid Response Elements region

Question 29

What are the symptoms of Hypothyroidism?

Answer 29

DOGSACS
Decreased Appetite
Obesity
Goitre
Sensitive to Cold
Alopecia
Constipation
Slow/Lethargic