Brainscape's Knowledge GenomeTM

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


See full index

Endocrinology > Thyroid Pharmacology > Flashcards

Thyroid Pharmacology Flashcards

1
Q

What are the relative half lives and potency of thyroid hormone?

A

T4: half life is 7 days
T3: half life is only 1 day but it is 4x more potent

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

Are there greater levels of free T4 or free T3? About how much is there?

A

There is about 10x more free T3. Unbound T3 constitutes .4% of the total thyroid hormone

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

What are the three classes of thyroid hormone preparations?

A

Levothyroxine: LT4
Liothyronine: LT3
T4/T3 Mixes: just don’t use them

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

Why is hypothyroid treated with T4? (2)

A

Longer half life and peripheral conversion via deiodination

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

When is T3 use indicated? (2)

A

Myxedema coma

Withdrawal for thyroid cancer radioactive iodine treatment

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

When do you see side effects from thyroid treatment?

A

Only from inappropriate dosing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some dosing considerations when starting therapy?

A

Starting dose depends on age, degree of thyroid failure of patient

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

How often is TSH levels monitored?

What is the target range? Does this change for people of different ages?

A

Check TSH about every 6 weeks

Target TSH normal range (.5-5) with target usually below 2.5. The target is usually higher in older people

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

What are reasons for TSH levels being higher than expected? (6)

A 
Noncompliance
Drugs that decrease LT4 absorption
Conditions that decrease LT4 absorption: SI disease
Drugs that increase LT4 metabolism
Increased TBG
Progression of thyroid disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name some drugs that increase LT4 metabolism.

Name some factors that increase TBG

A

Drugs: phenytoin, rifampin, phenobarbital, carbamazepine

Increased TBG seen during pregnancy, estrogens, hepatitis

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

Why would TSH on therapy be lower than expected? (5)

A 
Dopamine
High dose glucocorticoids
Decreased TBG
Self-administration of excess LT4
Reactivation of Grave's disease or development of autonomous nodules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are some factors that decrease TBG? (4)

A

Androgens
Nephrotic syndrome
Chronic liver disease
Severe systemic illness

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

What are drugs that cause hypothyroidism? (5)

A

Primary: amiodarone, lithium, INFa, aminoglutethimide

Secondary bexarotene

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

For what conditions should you involve a endocrinologist to monitor TSH levels? (2)

A

Pregnancy

Thyroid cancer

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

What do you do to treat myxedema coma? Why?

A

First IV hydrocortisone to fix adrenal

Give LT4/LT3 IV–decreased metabolism for most medications

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

What is the mechanism of antithyroid drugs?

A

interfere with two steps of thyroid hormone synthesis via TPO

  1. Intrathyroidal iodine utilization
  2. Iodotyrosine coupling
17
Q

When do you use antithyroid drugs?

A

Graves disease

To cool patient down prior to RAI or surgery

18
Q

What are two antithyroid drug? Which is preferred? Why? (3)

A

PTU and Methimazole.
Mithimazole has longer half life– longer duration of action.
Mithimazole is not protein bound.
PTU decreases T4-T3 conversion

19
Q

When do you use methimazole? When do you use PTU? (3)

A

Use methimazole in all Grave’s disease patients except:
First trimester of pregnancy
Thyroid storm
AE to methimazole

20
Q

What are the main side effects of antithyroid drugs? (6)

A

Agranulocytosis, severe hepatitis (just PTU), cholestasis (MMI), vasculitis, polyarthritis, skin rxns

21
Q

What is the greatest concern with antithyroid drugs?

How is it monitored?

A

Agranulocytosis, which occurs in .1-.5% patients at any time.

They should stop antithyroid drug and check WBC if fever or sore throat.

22
Q

Which drugs inhibit T4-T3 conversion? (3)

A

PTU
Glucocorticoids
Propanolol

23
Q

Which other drugs can you use in hyperthyroidism? (3)

A

Beta-blockers
NSAIDs in subacute thyroiditis
Iodine/glucocorticoids in severe thyrotoxicosis

24
Q

Which drugs do you use in treatment of Thyroid Storm? (4)

A

PTU
Propanolol or esmolol
Hydrocortisone
Potassium iodide drops

25
Q

How is iodide uptake mediated? How does it correspond to dietary supply?

A

Iodide uptake is mediated by the Na/I symporter (NIS).

Low iodide increases NIS; high iodide decreases NIS

26
Q

Where is NIS expressed?

A

High levels in thyroid

Low levels in salivary glands, lactating breast, placenta

27
Q

What is optimal iodide intake? What are effects of prolonged decrease? (2)

A

Optimal intake is 100-150 mcg/day

Prolonged decrease results in endemic goiter and cretinism

28
Q

What is the Wolff-Chaikoff Effect? What is the clinical implication?

A

Excess iodide transiently inhibits thyroid iodide organification.

In individual with normal thyroid, gland escapes inhibitory effect. But if underlying autoimmune thyroid disease, suppressive effect may persists.

29
Q

What is the Jod-Basedow Phenomenon? When is it observed?

A

The Jod-Basedow Phenomenon describes thyrotoxicosis produced by iodine exposure.

It occurs in nodular thyroid glands

30
Q

Describe the uses for radioiodine. (2)

When is it contraindicated

A

Can be used in low doses for diagnostic purposes or high doses for therapy

It should not be given to breast-feeding/pregnant women or children

31
Q

When do you use radioiodine therapy? What is the long-term effect?

A

Use it in Grave’s disease to create hypothyroidism. The result of radioiodine therapy is necrosis of follicular cells followed by disappearance of colloid and fibrosis of gland

32
Q

What is amiodarone?

A

Drug used to treat arrhythmias

33
Q

Describe the iodine effect of amiodarone: when do you observe it?

A

In patients with underlying thyroid nodular disease or Grave’s disease, amiodarone results in increased thyroid hormone production.

This is called the iodine effect

34
Q

Describe the direct toxic effect of amiodarone: when do you observe it?

A

In patients with normal thyroids it induces destructive thyroiditis–>
There is increased release of preformed thyroid hormone from colloid

35
Q

When do you use recombinant TSH?

A

Use in thyroid cancer patients: stimulate thyroid tissue for diagnostic thyroglobulin measurement and radioiodine scanning.

It avoids symptomatic hypothyroidism from radioiodine

36
Q

When does amiodarone cause hypothyroidism?

A

In patients with predisposition for hypothyroidism such as Hashimotos

Endocrinology (26 decks)

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