Thyroid Hormones

Question 1

Where in the Thyroid is Thyroglobulin stored?

Answer 1

1. Follicle Lumen

Question 2

What is synthesized in the Follicle Cells?

Answer 2

1. T3 and T4.

Question 3

How does I- (Iodide) uptake occur on the follicular cell?

Answer 3

Na-I- Symporter (NIS)

Question 4

Drugs that inhibit the Na-I - symporter?

Answer 4

1. Perchlorate

2. Thiocyanate

Question 5

Functions of Thyroperoxidase (TPO)?

Answer 5

1. Oxidation: I- to Io
2. Organification: Monoiodotyrosine (MIT) and Diiodotyrosine (DIT)
3. Coupling: DIT + DIT= T4 and DIT + MIT= T3

Question 6

Most abundant thyroid hormone and why?

Answer 6

T4; greater half life (6 days)

Question 7

Most active thyroid hormone and why?

Answer 7

T3; higher affinity to nuclear receptor.

Question 8

Drugs that inhibit TPO?

Answer 8

1. Methimazole

2. Propylthiouracil (PTU)

Question 9

Conditions that secrete thyroglobulin ?

Answer 9

1. Thyroid cancer
2. Thyroiditis
3. Nodular Goiter

Question 10

How are most of the thyroid hormones transported?

Answer 10

1. TBG (thyroid-binding globulin)

Question 11

Peripheral conversion of T4 —> T3?

Answer 11

5’-deiodinase

Question 12

Thyroid hormones main function?

Answer 12

1. ⬆️Basal Metabolic Rate (⬆️NaKATPase)
2. ⬆️Bone Growth
3. ⬆️Brain Maturation
4. ⬆️Beta-adrenergic effects: ⬆️SV ⬆️HR and ⬆️CO and ⬇️TPR.
5. Break down of Lipids: Lipolysis
6. ⬆️Blood Sugar (glycogenolysis and gluconeogenesis)
7. ⬆️GI motility

Question 13

Main site for thyroid negative feedback?

Answer 13

Anterior Pituitary

Question 14

How does the negative feedback work at the level of the anterior pituitary?

Answer 14

1. ⬇️TRH sensitivity in the thyrotrophs.

Question 15

What are the long term effects of TSH stimulation on thyroid?

Answer 15

1. ⬆️Blood flow

2. ⬆️Hypertrophy and ⬆️Hyperplasia