Guyton Thyroid Hormones

Question 1

What are the 2 thyroid metabolic hormones?

Answer 1

thyroxine (T4), triiodothyronine (T3)

Question 2

Compare the 2 thyroid hormones by their production quantities, circulating cc and tissue function potency

Answer 2

mostly produces thyroxine (T4), which circulates in the plasma –> T3 more potent activity (4 to1?) –> converted to T3 before reaching tissue cells

Question 3

Explain the structures of the thyroid gland that produce thyroid hormones

Answer 3

large number of follicles in the thyroid gland –> filled with colloid and lined with cuboidal epithelial cells

colloid: mostly made of thyroglobulin -> contain/bind thyroid hormones

Question 4

How are thyroid hormones stored?

Answer 4

in thyroglobulin

Question 5

How are thyroid hormones transported through the circulation?

Answer 5

99% protein bound
* thyroxine-binding globulin (most)
* thyroxine-binding prealbumin
* albumin

Question 6

What tissues/cells do thyroid hormones exert effects on?

Answer 6

any

Question 7

Explain the steps of thyroid hormones genomic effects

Answer 7

diffuses into the nucleus –> thyroid response elements –> affects transcription –> protein production

Question 8

List effects of thyroid hormones on body function

Answer 8

• increased number and activity of mitochondria
• increased Na/K/ATPase activity
• increased carbohydrate metabolism (increased cellular glucose uptake, glycolysis, gluconeogenesis, increased insulin secretion)
• increased fat metabolism –> decreasing fat stores (increased FFA, but decreased cholesterol and triglycerides)
• increased blood flow and cardiac output
• increased basal metabolic rate

Question 9

List the 5 effects of TSH on thyroid secretion/production

Answer 9

• increased proteolysis of thyroglobulin –> releasing thyroid hormones
• increased iodide pump activity
• increased iodination of tyrosine
• increased size and secretory activity of the thyroid cells
• increased number of thyroid cells