Thyroid Disorders Exam 1

Question 1

Where does T3/T4 come from?

Answer 1

they are made in the colloid of the follicular cells

Question 2

Explain the production of T3/T4

Answer 2

• TSH levels stimulate Na+/I- symporter and insert it in thyroid follicle
• Thyroid peroxidase oxidizes I- to get ready for production
• Thyroid peroxidase iodinates tyrosine residues where T3/T4 is formed

Question 3

How are levels of T3/T4 regulated?

Answer 3

• when body recognizes that it needs more T3, it converts T4 to T3
• most of the T4-T3 conversion happens in the liver

Question 4

Physiological functions of T3

Answer 4

• Metabolic
• Development
• Nervous system
• Cardiovascular

Question 5

Physiological functions of T3

Answer 5

• Metabolic
• Development
• Nervous system
• Cardiovascular

Question 6

Physiological functions of T3: Metabolic

Answer 6

• Increase O2 consumption
• Produces heat
• Increases basal metabolic rate

Question 7

Physiological functions of T3: Development

Answer 7

• Growth and nervous system function (Cretinism)

* Important for development of fetus

Question 8

Physiological functions of T3: Nervous system

Answer 8

• Myelination (reflex)

* Brain – mood, memory, wakefulness

Question 9

Physiological functions of T3: Cardiovascular

Answer 9

• Increased beta-adrenergic receptors
• Increased catecholaminergic response
• Increases LDL receptors in liver, thus lowering cholesterol

Question 10

What can be use to treat hypothyroidism?

Answer 10

• Levothyroxine
• Liothyronine
• Thyrolar
• Dessicated thyroid

Question 11

Levothyroxine

Answer 11

• Supplies body with T4 and body will convert it to T3 when it needs it
• Long half life -> once daily dosing
• Decrease adverse effects vs. administering T3 itself
• Stick to one brand because they’re not all the same
• Food affects absorption (decrease) can take with food but have to be consistent

Question 12

Liothyronine

Answer 12

• No conversion needed; T3
• Fast onset of action
• Good for those who are deficient in de-iodinase because unable to convert from T4 to T3
• Short half life -> more frequent dosing
• Too much T3 will result in adverse effects similar to hyperthyroidism

Question 13

Thyrolar

Answer 13

• T4:T3 -> 4:1 ratio

- No documented advantage

Question 14

Dessicated thyroid

Answer 14

• combination of T3 and T4 and other thyroid products

- animal products -> possible allergic reaction

Question 15

What can be use to treat hyperthyroidism?

Answer 15

• Thioamides
• Potassium iodide
• Iodine (131)

Question 16

Thioamides

Answer 16

• MOA: inhibits thyroid peroxidase -> shuts down T3/T4 production
• Ex. Methimazole (MMI) and propylthiouracil (PTU)
• PTU also inhibits deiodinase in the periphery -> works much faster
• Adverse effects: agranulocytosis; PTU – black box warning hepatotoxicity

Question 17

Potassium iodide

Answer 17

• Shuts down thyroid gland; shuts down production of T3/T4

- Can delay ability to use Iodine (131) -> do NOT give Iodine (131) after administering potassium iodide

Question 18

Iodine (131)

Answer 18

• Chemical radiation that selectively targets the thyroid gland
• Adverse effect that this may have is negative effects on salivary glands because they concentrate it as well
• Adverse effects: radioactivity, hypothyroidism
• Do not have human contact during this
• Contraindication: pregnancy

Question 19

Which of the following is the most physiologically active form of thyroid hormone? 
A. triiodothyronine
B. thyroxine
C. diiodotyrosine 
D. monoiosotyrosine

Answer 19

A. triiodothyronine

Question 20

What is the enzyme that facilitates oxidation and organification? 
A. Deiodinase 1
B. Deiodinase 2
C. Thyroid peroxidase 
D. Tyrosine hydroxylase

Answer 20

C. Thyroid peroxidase

Question 21

Which of the following statesments about thyroxine (T4) is true?
A. Thyroxine is formed by deiodinase, mostly in the periphery
B. Thyroxine has a short half-life compared to T3
C. Thyroxine is produced in equal amounts to T3 by the thyroid
D. Thyroxine is predominantly protein bound in blood

Answer 21

D. Thyroxine is predominantly protein bound in blood

Question 22

Which of the following drugs and formulations is correct?
A. Levothyroxine = T3
B. Liothyronine = T4 & T3 (4:1 ratio)
C. Thyrolar = T3
D. Dessicated thyroid = ground up animal thyroid

Answer 22

D. Dessicated thyroid = ground up animal thyroid

Question 23

Stacy has always taken her Synthroid with her breakfast. Dr. Oz told her on empty stomach only.
A. Yes, empty stomach only
B. No, no effect of absorption based on food
C. Yes, absorption affected by food, but maintain her routine

Answer 23

C. Yes, absorption affected by food, but maintain her routine

Question 24

Patient on liothyronine complains of sweatiness and racing heart. What do you suggest?
A. Check thyroid levels with doctor. Med dose may be too high
B. Check thyroid levels with doctor. Med levels may be too low
C. Probably just dehdydrated. Drink more water!
D. Switch to dessicated thyroid

Answer 24

A. Check thyroid levels with doctor. Med dose may be too high

Question 25

\_\_\_\_\_\_\_\_\_ inhibits thyroid peroxidase and deiodinase 1 in periphery. 
A. Methimazole 
B. Propylthiouracil 
C. Potassium iodide 
D. 131 I

Answer 25

B. Propylthiouracil

Question 26

131 I is most effective when used immediately after high doses of potassium iodide.
A. True
B. False

Answer 26

B. False