TH Synthesis and Regulation

Question 1

What are the three fundamental physiologic processes affected by thyroid hormones?

Answer 1

• Cellular differentiation
• Growth
• Metabolism

These processes are crucial for normal development and functioning of the body.

Question 2

What is the primary function of the thyroid gland?

Answer 2

Synthesis and secretion of thyroid hormones

The thyroid gland plays a critical role in regulating metabolism and energy balance.

Question 3

What are the major building blocks involved in thyroid hormone synthesis?

Answer 3

• Tyrosine
• Iodide (I-)

These components are essential for the production of thyroid hormones.

Question 4

What is the function of thyroglobulin (TGB) in thyroid hormone synthesis?

Answer 4

Acts as a scaffold for the incorporation of tyrosines

TGB is a glycoprotein that contains multiple tyrosine residues used to produce thyroid hormones.

Question 5

True or False: Iodide deficiency can impact HPT regulation and thyroid hormone synthesis.

Answer 5

True

A lack of iodide can lead to insufficient production of thyroid hormones and related disorders.

Question 6

What hormone stimulates all steps involved in thyroid hormone synthesis?

Answer 6

Thyroid Stimulating Hormone (TSH)

TSH is secreted by the anterior pituitary and acts on the thyroid gland to regulate hormone production.

Question 7

Fill in the blank: The thyroid gland develops from the _______ during embryonic development.

Answer 7

tongue root

This anatomical origin is important for understanding thyroid gland location and function.

Question 8

What are the two principle raw materials required for thyroid hormone synthesis?

Answer 8

• Tyrosine
• Iodide (I-)

Both materials are crucial for the production of T3 and T4 hormones.

Question 9

What condition is characterized by an enlarged thyroid gland due to iodine deficiency?

Answer 9

Goiter

Goiter is often linked to hypothyroid states and over-stimulation of the thyroid gland by TSH.

Question 10

What cells in the thyroid gland produce calcitonin?

Answer 10

Parafollicular or C cells

Calcitonin is involved in calcium metabolism and helps regulate calcium levels in the blood.

Question 11

What are the key steps in thyroid hormone synthesis? List them.

Answer 11

• Uptake of iodide by thyroid follicle
• Iodide efflux into colloid via pendrin
• Oxidation to iodine by thyroid peroxidase (TP)
• Thyroglobulin synthesis and exocytosis
• Iodination of tyrosine residues via TPO
• Coupling of MIT and DIT on TGB
• Endocytosis of TGB into follicular epithelial cell
• Release of T4 and T3 into bloodstream

These steps outline the complex process of synthesizing thyroid hormones.

Question 12

What is the main source of dietary iodide?

Answer 12

Iodized salt

Other sources include seafood and plants grown in iodine-rich soils.

Question 13

What is the role of the sodium-iodide symporter in thyroid hormone synthesis?

Answer 13

Facilitates the uptake of iodide from blood into thyroid epithelial cells

This process is crucial for maintaining adequate levels of iodide for hormone production.

Question 14

How does the thyroid gland regulate iodide concentration?

Answer 14

By using Na/K-ATPase to maintain sodium concentration gradient

This gradient allows for effective iodide uptake and transport within the gland.

Question 15

What is the primary carrier protein for thyroid hormones in the blood?

Answer 15

Thyroxine-binding globulin (TBG)

TBG helps transport thyroid hormones, which are poorly soluble in water, throughout the bloodstream.