Zheng RS 1- Thyroid Physiology

Question 1

What structure does the isthmus and lateral lobes of the thyroid gland develop from?

Answer 1

Thyroglossal duct

Question 2

How long can thyroid hormone be stored for?

Answer 2

2-3 months

Question 3

On what protein are T4 and T3 created on? What enzyme is responsible for this process?

Answer 3

On thyroglobulin, thyroid peroxidase ill convert two molecules to T4 and T3

Question 4

How is thyroid hormone transported in the blood? What percentage is transported via a carrier? Where is the carrier produced?

Answer 4

Thyroxine binding protein is responsible for the transport of 80% of thyroid hormone in the blood, and it is synthesized in the liver.

Question 5

Around what percentage of receptor binding is T3 responsible for? How is T4 converted to T3?

Answer 5

T3 accounts for around 90% of TH receptor binding.

T4 is converted to T3 by deiodinase in target cells

Question 6

What is the Wolff-Chaikoff effect? What is a clinical application?

Answer 6

Large amounts of iodine will inhibit thyroid hormone synthesis.

This can be a treatment for hyperthyroidism

Question 7

What is the most common cause of hypothyroidism?

Answer 7

Auto-immune disease, such as Hashimoto’s disease

Question 8

What is the most common cause of hyperthyroidism? What is the mechanism of action of this disease?

Answer 8

Graves disease, which is an autoimmune disorder in which antibodies stimulate the TSH receptor, causing excess TH

Question 9

What is the best initial test of thyroid function? Best test for hyperthyroidism? Hypothyroidism?

Answer 9

The best initial test of thyroid function is serum TSH.

The best test for hyperthyroidism is serum T3 (FT3)

The best test for hypothyroidism is serum T4 (FT4)