Exam 5: Thyroid Physiology Flashcards Preview

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Flashcards in Exam 5: Thyroid Physiology Deck (27)
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1
Q

What is required for T3/T4 synthesis?

A

Iodide

2
Q

What is iodide absorbed from?

A

GI tract

3
Q

What is iodide excreted by?

A

Kidney

4
Q

Where does iodide uptake occur?

A

Thyroid gland

Salivary gland

5
Q

Describe the iodide pump of the thyroid gland

A
Active transport (energy dependent)
Concentration gradient up to 250x
6
Q

What is the uptake of iodide by the thyroid gland dependent on?

A

TSH

7
Q

What does thyroid peroxidase play a role in?

A

Iodide oxidation
Organification
Coupling

8
Q

Which is more active, T3 or T4?

A

T3

9
Q

What makes T3 more active?

A

It enters the cell more rapidly and it is more potent

10
Q

How much T3 is made in the thyroid? Where does the rest come from?

A

20%

De-iodination of T4 in tissues

11
Q

What is necessary for T3 and T4 transport?

A

Protein-binding

12
Q

What percentage of T3 and T4 are protein bound?

A

99%

13
Q

What determines that half life of thyroid hormone?

A

Binding affinity

14
Q

Which type of hormone is active, bound or free?

A

Free

15
Q

What is the biologically active version of thyroid hormone?

A

Free T4

Free T3

16
Q

How does thyroid hormone effect metabolism?

A

Increases metabolic rate, which increases oxidative phosphorylation in mitochondria

17
Q

What are the catabolic effects of thyroid hormone?

A

Lipolysis
Protein
Carbohydrate utilization, GI absorption

18
Q

What does thyroid hormone do to gastrointestinal motility?

A

Increases it

19
Q

How does thyroid hormone effect the cardiovascular system?

A

Stimulation of cardiac β-adrenergic receptors (increase HR, CO)
Increase GFR
Stimulates erythropoiesis

20
Q

How does thyroid hormone effect the neuromuscular system?

A

Increase mental alertness

Necessary for normal growth and neuronal development

21
Q

What does the hypothalamus receive input from?

A

Higher centers in the brain and body

22
Q

What hormone comes from the hypothalamus in the HPT axis?

A

Thyroid releasing hormone (TRH)

23
Q

What does TRH do?

A

Increase thyroid stimulating hormone (TSH)

24
Q

What hormone comes from the pituitary gland in the HPT axis?

A

TSH

25
Q

What does TSH do?

A

Binds to TSH receptors in thyroid, which stimulates the synthesis of T3 and T4

26
Q

What hormones come from the thyroid in the HPT axis?

A

Thyroid hormones (T3, T4)

27
Q

Describe thyroid hormone

A

Free hormone only
Inhibits TRH and TSH secretion
Increased T4 decreases TRH and TSH

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