Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

[OS 215] Endo Exam 2 Flo Cluster > Lec 06: Anti-Thyroid Drugs > Flashcards

Lec 06: Anti-Thyroid Drugs Flashcards

1
Q

True or False: thyroid problems are easier to treat than diabetes.

A

True.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Most basic principle when treating hypothyroidism.

A

Administering exogenous T4 or T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

4 basic modes of treating hyperthyroidism?

A

RADS

Radioactive Iodine - especially for long-term diseases like Graves’

Adjuncts - beta-blockers, corticosteroids, iodides

Drugs - Thionamides (aka Thioureylenes)

Surgery - reserved for nodules that are suspicious for cancer (usually non-functioning), really large goiters, pregnant and breastfeeding thyroid patients & those with allergy to medications.

  • For functioning nodules - 1st line: Drugs. If unresponsive: Radioactive Iodine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does the thyroid gland regulate?

A

The thyroid gland maintains metabolic homeostasis by regulating:

  • Growth and Development
  • Body Temperature
  • Energy Levels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Thyroid hormone-Immunoglobulin ratio of T4?

A

T4 has a higher thyroglobulin ratio than T3 (1) signifying that there is more T4 than T3 in the blood (However, protein-bound hormones are inactive). T3 is more peripherally active and more potent than T4.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 6 Major Steps in Thyroid Hormone synthesis?

A
  1. IODIDE TRAPPING - Active Transport of Iodine across the basement membrane
    into the thyroid cell (iodide trapping). Remember that there is
    a symporter across the cell membrane that transports iodine
    intracellularly.
  2. OXIDATION - (Inside the cell): Oxidation of iodide & iodination of tyrosyl
    residues in thyroglobulin. Result: monoiodothyroxines.
  3. COUPLING of MIT (monoiodotyrosine) molecules within thyroglobulin to form T3 and T4
  4. PROTEOLYSIS OF TG (Thyroglobulin) - release of free iodothyronines & iodotyrosines from colloid droplets (pinocytosis). They then find their way to the circulation.
  5. DEIODINATION of Iodotyrosines within the thyroid cells & recycling of iodine.
  6. T4 TO T3 - Intrathyroidal 5’-deiodination of T4 to T3
    * The peripheral conversion of T4 to T3 is an important step and is the target of action of many anti-thyroid drugs.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The basic substrate of thyroid hormone biosynthesis:

A

Iodine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Catalyzes the coupling of two molecules of DIT to form T4, and one molecule each of MIT and DIT to form T3.

A

Thyroid peroxidase (TPO)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The thyroid gland removes how many milligrams of iodide absorbed in the GIT from the extracellular pool?

A

75 mg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

During what steps in thyroid hormone synthesis is TPO active?

A

Step 2: OXIDATION (end result: MIT) and Step 3: COUPLING (of MIT molecules to form T3 and T4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What percent of T3 is unbound from TBGs?

A
  1. 3%.

* T4 = 0.03% which implies that T3 is more metabolically active

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Converts T4 to T3 in peripheral tissues.

A

iodothyronine 5’-deiodinase (found mainly in liver, thyroid and kidneys)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

True or False: Exogenous thyroid therapy us usually given as T3 since it is more metabolically active.

A

False.

Exogenous thyroid therapy is usually given as T4 to
simulate normal physiologic processes. If you give T3 directly, patients will suffer from more adverse drug reactions (ex. palpitations)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

True or False: T4 has a longer half-life than T3.

A

True. T1/2 of T4 is 7 days ans T3 is 1 day.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

True or False: In terms of daily production T3>T4.

A

False. Daily production of T3 = 25 mg, T4 = 75mg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

True or False: In terms of daily metabolic clearance, T3>T4

A

True. T3 is more metabolically active so logically, clearance is much higher (24L) compared to T4 (1.1L).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Thionamides act on which step/s of thyroid hormone synthesis?

A

OXIDATION and COUPLING

  • Same as TPO since thionamides block TPO!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which drugs inhibit colloid resorption and proteolysis of TGs?

A

Iodine & Lithium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

This occurs during excessive iodine intake leading to impediment of transport and release of thyroid hormones.

A

Wolff-Chaikoff effect.

*Opposite is Jod-Basedow phenomenon where excessive iodine intake aggravates hyperthyroidism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Large amounts of iodine and thiocyanates impede what step in thyroid hormone synthesis?

A

Iodide Transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where is TRH secreted?

A

Paraventricular nuclei in hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

INCREASE or DECREASE in thyroid hormones:

STRESS

A

DECREASE.

Stress is a negative inhibitor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

INCREASE or DECREASE in thyroid hormones:

High iodine levels

A

DECREASE (to some extent - Wolff-Chaikoff effect) then INCREASE (Jod-Basedow phenomenon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

INCREASE or DECREASE in thyroid hormones:

You have a cold.

A

INCREASE.

Cold sends signals to the hypothalamus, stimulating TRH production.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

INCREASE or DECREASE in thyroid hormones:

Increased somatostatin/steroids/dopamine

A

DECREASE.

These three inhibit TRH.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

The superfamily of nuclear receptors to which T3 receptors belong.

A

c-erb.

*Also includes receptors for steroid hormones, vitamins A & D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

TR monomers interact with retinoic acid X receptors to form:

A

TR:RXR heterodimers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How does the TR:RXR heterodimer inhibit gene expression?

A

by associating with a co-repressor complex that binds to DNA, IN THE ABSENCE OF T3.

  • In the presence of T3, the co-repressor complex dissociates and coactivators form to stimulate gene expression.
29
Q

HYPER- or HYPO- thyroidism?

myxedema

A

HYPO-

30
Q

HYPER- or HYPO- thyroidism?

Increased sweating

A

HYPER-

31
Q

HYPER- or HYPO- thyroidism?

Weight gain

A

HYPO-

32
Q

HYPER- or HYPO- thyroidism?

Osteoporosis

A

HYPER-

33
Q

Most common cause of hypothyroidism in the Philippines:

A

Post-procedural hypothyroidism

34
Q

Correct dose per kilogram of thyroid hormone replacement therapy.

A
  1. 6 to 1.7 mcg/kg with drus given in multiples of 25 mcgs.

* 100 mcg in a 65kg person.

35
Q

What should you do when giving hormone replacement therapy to elderly patients or those with CAD or arrhythmias?

A

SLOW replacement (titrate the dose)

36
Q

True or False: You don’t give thyroid hormone replacement therapy to pregnant patients.

A

False. Continue giving thyroid hormones to avoid congenital hypothyroidism in the child (cretinism)

37
Q

Dosage of thyroid hormone replacement for suppression of thyroid CA.

A

2.2 - 3.0 mcg/kg

38
Q

Preparation of choice for replacement and suppression therapy.

A

Synthetic Levothyroxine

39
Q

Toxic multinodular goiter is also known as:

A

Plummer’s disease

40
Q

Most common cause of thyrotoxicosis:

A

Graves’ disease (Diffuse toxic goiter) - 60-80%

41
Q

The pro-drug of methimazole:

A

carbimazole

42
Q

True or False: Thionamides are rapid onset drugs.

A

False. There is SLOW onset of action since it merely prevents formation of new hormones, meaning preformed hormones can still take effect.

43
Q

The preferred drug for treatment of thyroid storm.

A

Propylthiouracil (PTU)

50mg dose, T1/2: 1.5 hours

*Preferred because of its effect on T4 to T3 conversion in peripheral tissues.

44
Q

True or False: Methimazole is the antithyroid drug of choice.

A

True. Although PTU is preferred for thyroid storm and is cheaper, PTU can lead to excessive hepatic risks. Methimazole is also 10x more potent.

45
Q

Most common adverse reaction in using thionamides.

A

Maculopapular pruritic rash (20%)

46
Q

What to do when the patient experiences agranulocytosis while using thionamides?

A

Discontinue drug right away.

47
Q

True or False: if the patient experiences agranulocytosis when using Methimazoles, stop the drug immediately and use PTU instead.

A

False.

  • If life-threatening side effects result, NEVER reintroduce the
    precipitating agent and DO NOT use other thionamides since
    there is high degree of cross-reactivity.
  • If minor side effects only, patient can continue but with antihistamine, lower dose, or shift to another drug.
48
Q

What to watch out for when using iodides.

A

angioedema

49
Q

Potassium perchlorate is no longer used clinically because it can cause:

A

aplastic anemia

50
Q

Most common adverse reaction with potassium iodide solution use.

A

Acneiform rash

51
Q

Used in the past to decrease size and vascularity of hyperplastic thyroid glands in Graves’ disease.

A

Potassium Iodide Solution.

52
Q

True or False: You can use corticosteroids to treat adrenal insufficiency in patients with thyroid storm.

A

True.

*Corticosteroids inhibit peripheral conversion of T4 to T3 (like B-adrenergic Receptor Blocking Drugs and PTU)
It can also suppress thyroid-stimulating antibodies (Graves)
It is also Antipyretic.

53
Q

True or False: It is better to select non-cardiac selective beta-adrenergic receptor blocking drugs for asthmatic patients.

A

False. You don’t use beta-adrenergic receptor blocking drugs on asthmatic patients.

54
Q

How long does it take thionamides to deplete T4 stores?

A

3-4 weeks

55
Q

True or False: Potassium iodide solution must be given in high doses to inhibit iodide transport effectively.

A

True. If given in small microgram doses, it actually enhances thyroid hormone synthesis which can easily worsen thyrotoxicosis.

56
Q

Radioisotope used in Radioactive Iodine Therapy:

a. Iodine123
b. Iodine69
c. Iodine6969
d. Sexboy69

A

a. Iodine123

* Iodine123 or Iodine131

57
Q

For how many months should a patient avoid pregnancy after undergoing Radioactive Iodine Therapy?

A

6-12 months

58
Q

RAI is more preferred over surgery in Graves’ disease.

A

True.

59
Q

How do high levels of iodide reduce thyroid hormone release?

A

By inhibiting thyroglobulin proteolysis

60
Q

Which of the following anions compete with Iodide uptake?

a. ClO4-
b. TcO4-
c. SCN-
d. AOTA

A

d. AOTA

ClO4- (perchlorate)
TcO4- (pertechnetate)
SCN- (thiocyanate)

61
Q

A patient diagnosed with hyperthyroidism is currently taking
PTU 50 mg 2 tablets 3x a day. His recent Free T4 result is
already normal. He requests that you change his medication
because he finds PTU very bitter and tend to forget to take his
last dose for the day. You decide to prescribe methimazole which
is in the 5mg tablet preparations. How many tablets of
methimazole should you give that is equivalent to the current
dose of PTU?

a. 3 tablets
b. 9 tablets
c. 6 tablets
d. 12 tablets

A

c. 6 tablets

Current PTU dose = 50mg x 2 tablets x 3/ day = 300 mg/day.

Methimazole is 10x more potent than PTU so you only need 30mg/day = 6 5mg tablets per day.

62
Q

What drug acutely inhibits the release of preformed thyroid
hormone, making it very useful in the treatment of thyroid storm?

a. PTU
b. Propanolol
c. iodide
d. Dexamethasone.

A

c. iodide
* It’s not a because, remmber: thionamides only prevent formation of new hormones but have no effect on preformed hormones. Iodides on the other hand are useful in this aspect because of the Wolff-Chaikoff effect.

63
Q

Thionamide drug that inhibits peripheral conversion of T4 to
T3

a. Methimazole
b. Carbimazole
c. Propylthiouracil
d. All of the above

A

c. PTU

64
Q

Attenuate(s) or reduce serum concentrations of thyrotropin
receptor antibodies

a. Methimazole
b. Carbimazole
c. Propylthiouracil
d. All of the above

A

d. AOTA

65
Q

Preferred agent in thyroid storm

a. Methimazole
b. Carbimazole
c. Propylthiouracil
d. All of the above

A

c. PTU

66
Q

Inhibit(s) organification of iodides and coupling of iodothyronines

a. Methimazole
b. Carbimazole
c. Propylthiouracil
d. All of the above

A

d. AOTA

* organification = oxidation

67
Q

Used to prepare patient for definitive treatment such as RAI
ablation.

a. Methimazole
b. Carbimazole
c. Propylthiouracil
d. All of the above

A

c. PTU

68
Q

The drug of choice for the OPD medical treatment of patients
with hyperthyroidism:

a. Propylthiouracil
b. Beta-blockers
c. High dose iodides
d. Methimazole

A

d. Methimazole

[OS 215] Endo Exam 2 Flo Cluster (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions