Thyroid Gland

Question 1

Conversion of elemental iodide to organic happens at which organs?

Answer 1

the stomach and the upper small intestine

Question 2

True or False:
Excretion of iodide is through the kidneys via complete glomerular filtration or passive reabsorption, both of which are independent of the serum concentration of iodide

Answer 2

True

Question 3

An active symporter allowing iodine to enter follicular cells from the blood stream

Answer 3

SODIUM IODIDE TRANSPORTER

Question 4

Chloride/iodide ion counter transporter that enables iodide to exit the thyroid cells across the apical membrane into the follicle.

Answer 4

Pendrin

Question 5

Enzyme that acts as a “thyroid axis sensor” in the thyrotropes of the pituitary

Answer 5

TYPE 2 DEIODINASE (D2): 5’/3’ Deiodinase

Question 6

Most T4 to T3 conversions happen through this enzyme

Answer 6

TYPE 1 DEIODINASE (D1): 5’/3’ Deiodinase

Question 7

Main deiodinase that increase in patients with hypothyroidism to maintain constant T3 levels in brain

Answer 7

D2

Question 8

• Inactivating deiodinase

* Converts T4 to inactive form, RT3

Answer 8

TYPE 3 DEIODINASE (D3): 5/3 Deiodinase

Question 9

Enzyme that is increased in patients with hyperthyroidism to blunt overproduction of T4

Answer 9

TYPE 3 DEIODINASE (D3): 5/3 Deiodinase

Question 10

Protein that Transports T4 in cerebrospinal fluid

Answer 10

Transthyretin (TTR)
→ Binds 15-20% of T4 or T3
→ Transports T4 in cerebrospinal fluid
→ Provides thyroid hormones to CNS

Question 11

Intraglandular concentration of iodide reaches a level that paradoxically suppresses TPO activity, a phenomenon called:

Answer 11

Wolf-Chaikoff Effect