Brainscape's Knowledge GenomeTM

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


See full index

Pharmacology > Thyroid Drugs > Flashcards

Thyroid Drugs Flashcards

1
Q

major steps in thyroid hormone synthesis

A
  1. Uptake of iodide ion (I–) by the thyroid gland.
  2. Oxidation of iodide to iodine.
  3. Iodination of tyrosyl groups of thyroglobulin.
  4. Coupling of iodotyrosine residues to generate the thyroid hormones.
  5. Resorption of the thyroglobulin colloid from the lumen into the cell.
  6. Proteolysis of thyroglobulin and the release of thyroxine and triiodothyronine into the blood.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

T_ acts more rapidly and is more potent than T_
because it is __ tightly bound to plasma proteins and binds more avidly to TH receptors

A

T3 acts more rapidly and is more potent than T4

because T3 is less tightly bound to plasma proteins and binds more avidly to TH receptors

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

physiological effects of thyroid hormone

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

mechanisms thyroid hormone is metabolized

A
  • Deiodination (most important)
  • Glucuronidation
  • Sulfation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Deiodination of T4 by ____ results in the production of either T3 (more potent than T4) or reverse T3 (metabolically inactive)

A

Deiodination of T4 by 5′deiodinase results in the production of either T3 (more potent than T4) or reverse T3 (metabolically inactive)

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

5′deiodinase inhibited by:

  1. Drugs such as (4)
  2. Severe illness and starvation
  3. Iodinated compounds such as the radiographic agents iopanoic acid and ipodate
A

5′deiodinase inhibited by:

  1. Drugs: propylthiouracil, propranolol, corticosteroids, amiodarone
  2. Severe illness and starvation
  3. Iodinated compounds such as the radiographic agents iopanoic acid and ipodate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

T4 and T3 are also conjugated in the ___ to form sulfates and glucuronides

These conjugates enter the __ and pass into the intestine where they are hydrolyzed

some are ___ (enterohepatic circulation), others are excreted in stool

A

T4 and T3 are also conjugated in the liver to form sulfates and glucuronide

These conjugates enter the bile and pass into the intestine where they are hydrolyzed

some are reabsorbed (enterohepatic circulation), others are excreted in stool

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

In the intestine, ____ (e.g. __) bind to and prevent the enterohepatic cycling of thyroid hormones

A

In the intestine, Bile acid sequestrants (e.g. cholestyramine) bind to and prevent the enterohepatic cycling of thyroid hormones

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

Deiodinase and UDP-glucuronosyltransferase enzymes are inducible, ___ the metabolism of T3 and T4

Enzyme inducer: ___

Clinical use for this?

A

Deiodinase and UDP-glucuronosyltransferase enzymes are inducible, increasing the metabolism of T3 and T4

Enzyme inducer: rifampin

Patients dependent on T4 replacement medication may require increased dosages to maintain clinical effectiveness if they are also on an enzyme inducer

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

clinical manifestations of hypothyroidism

A
  • goiter
  • muscle weakness, lethary
  • dry coarse skin and hair
  • yellowish tint of the skin
  • cold intolerance, cold skin
  • decreased sweating
  • thick tongue
  • delayed DTRs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

___ is the most common cause of hypothyroidism in the USA

___ is the most common cause worldwide

A

Hashimoto’s thyroiditis the most common cause of hypothyroidism in the USA

Iodine deficiency is the most common cause worldwide

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

list other causes of hypothyroidism

A
  • thyroidectomy
  • external neck irradiation
  • RAI therapy
  • drug-induced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Drugs that can cause hypothyroidism

A
  • Thioamides
  • Iodides
  • Amiodarone
  • Lithium
  • Aminoglutethimide
  • Rifampin
  • TKI’s (e.g., imatinib, sunitinib, sorafenib)
  • Interleukin 2
  • Interferon-α
  • Sulfonylureas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

treating amioderone-induced hypothyroidism

A

Levothyroxine even after amioderone discontinuance (bc of amioderones very long half-life)

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

Levothyroxine Vs. Liothyronine

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

Synthetic _____ is the preparation of choice for thyroid hormone replacement therapy

A

Synthetic levothyroxine (T4) is the preparation of choice for thyroid hormone replacement therapy

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

Thyroid replacement therapy AEs

A
  • hyperthyroid-like manifestations
  • ↑ risk of atrial fibrillation and osteoporosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

____ is a severe and long-standing form of hypothyroidism

describe cardinal features

A

Myxedema coma is a severe and long-standing form of hypothyroidism:

Hypothermia
Respiratory depression
Decreased consciousness

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

Management of myxdemea coma: IV ___

___ may be added until the patient is stable and conscious

A

Management of myxdemea coma: IV levothyroxine

Liothyronine may be added until the patient is stable and conscious

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

During pregnancy, adequate dose of ___ is important as early development of the fetal ___ depends on maternal thyroxine

A

During pregnancy, adequate dose of levothyroxine is important as early development of the fetal brain depends on maternal thyroxine

21
Q

A higher dose of levothyroxine is usually required in pregnant patients - why?

A
  1. ↑ [TBG] induced by estrogen
  2. Expression of 5′deiodinase 3 (D3) by the placenta
  3. Small amount of transplacental passage of levothyroxine from mother to fetus
22
Q

Congenital hypothyroidism treatment depends on the __ and ___ with which hypothyroidism is corrected

If ____ is instituted within ___, normal physical and mental development can be achieved

A

Congenital hypothyroidism treatment depends on the age and speed with which hypothyroidism is corrected

If levothyroxine is instituted within first 2 weeks of life, normal physical and mental development can be achieved

23
Q

Clinial features of hyperthyroidism

A
  • nervousness, heat intolerance
  • increased sweating, palpitations
  • fatigue, weakness, dyspnea
  • weight loss with increased appetite
  • signs: goiter with bruit over thyroid, tachycardia, skin changes and eye signs
24
Q

____ is most common cause of hyperthyroidism

Other causes?

A

Grave’s disease (toxic diffuse goiter) is most common cause of hyperthyroidism

  • toxic adenoma
  • toxic multinodular goiter
  • factitious hyperthyroidism
  • Drug-induced
25
Q

Drug-induced hyperthyroidism

A
  • Iodides
  • Amiodarone
  • Interleukin 2
  • Interferon-α
  • Lithium
26
Q

Drugs used in the management of hyperthyroidism

A
  • Thioamides
  • Iodides
  • β-antagonists
  • Glucocorticoids
  • Bile acid sequestrants
27
Q

Thiomides

A

Methimazole, Propylthiouracil (PTU)

28
Q

Methimazole, Propylthiouracil (PTU) inhibit formation of thyroid hormones by inhibiting ____

A

Methimazole, Propylthiouracil (PTU) inhibit formation of thyroid hormones by inhibiting thyroid peroxidase (oxidation, iondination, coupling)

29
Q

what effect does propylthiouracil have that Methimazole does not?

making PTU the preferred treatment of ____

A

Propylthiouracil can also inhibit conversion of T4 → T3

making PTU the preferred treatment of severe hyperthyroid and thyroid storm

30
Q

Thioamides clinical indications

A
  • hyperthyroidism
  • PTU: DOC for thryoid storm
  • In conjunction with radioactive iodine, to hasten recovery while awaiting the effects of radiation
  • Control hyperthyroidism in preparation for surgical treatment
31
Q

Thioimide AEs

A
  • Urticarial rash - most common
  • Agranulocytosis - most serious
  • Hypothyroidism
  • PTU
    • Severe hepatitis
    • Vasculitis
  • Methimazole
    • Teratogenic
32
Q

Methimazole is preferable to propylthiouracil except in ____

A

Methimazole is preferable to propylthiouracil except in the first trimester of pregnancy and thyroid storm

33
Q

Compare methimazole to propylthiouracil

A
  • Methimazole
    • less adverse effects
    • lower risk of serious liver injury
    • longer t1/2 DOA
      • 1x/day vs PTU 3/xday
34
Q

Iodides MOA

A

inhibit hormone release from thyroid gland through blocking thyroglobulin proteolysis and iondination - Wolff-Chaikoff effect

35
Q

Why should Iodide not be used alone?

A

thyroid gland escapes iodide block in 2–8 weeks → withdrawal can cause severe exacerbation of thyrotoxicosis in an iodine-enriched gland

36
Q

Clinical use of Iodides

A
  • Thyroid storm
    • rapid improvement of thyrotoxic symptoms
  • Preoperative preparation for surgery
    • decreases size and vascularity of hyperplastic thyroid glands
  • Radiation emergencies involving release of radioactive iodine isotopes
37
Q

Iodide AEs

A
  • uncommon
  • May precipitate hyperthyroidism (Jod-Basedow phenomenon) or hypothyroidism (failure to escape from the acute Wolff-Chaikoff effect)
  • Delay onset of thioamide therapy or prevent use of radioactive iodine therapy for several weeks
  • contraindicated in pregnancy: can cause fetal goiter
38
Q

thyroid hormones increase expression of ___ receptors → resulting in ___

A

thyroid hormones increase expression of β-adrenergic receptors → resulting in excess catecholamine manifestations

HTN, tachycardia, lid lag and retraction, tremor, excessive sweating, anxiety, nervousness

39
Q

____ are used extensively to alleviate catecholamine excess-like manifestations associated with hyperthyroidism and thyroid storm

A

B-blockers are used extensively to alleviate catecholamine excess-like manifestations associated with hyperthyroidism and thyroid storm

40
Q

___ inhibits conversion of T4 → T3

A

Propranolol inhibits conversion of T4 → T3

41
Q

what do we give to control tachycardia in patients in whom β blockers are contraindicated (e.g. COPD)

A

Diltiazem, Verapamil

42
Q

____ inhibit conversion of T4 → T3 and promote vasomotor stability

A

glucocorticoids inhibit conversion of T4 → T3 and promote vasomotor stability

43
Q

Glucocorticoides are used in the management of (3)

A
  • Thyroid storm
  • Grave’s ophthalmopathy (oral prednisone)
  • Dermopathy (topical)
  • possibly treat associated relative adrenal insufficiency
44
Q

In the intestine, ____ (3) bind to and prevent the enterohepatic cycling of thyroid hormones

used in the management of ___

A

In the intestine, bile acid sequestrants (cholestyramine, colestipol, colesevelam) bind to and prevent the enterohepatic cycling of thyroid hormones

used in the management of thyroid storm

45
Q

Preferred treatment for hyperthyroidism in patients without heart disease?

A

Radioiodine therapy (RAI) 131I

RAI destroys the thyroid parenchyma

46
Q

RAI AEs

A
  • causes permanent decreased thyroid activity
  • hypothyroidism
  • radiation thyroiditis
  • exacerbate Grave’s ophthalmopathy
  • destroys fetal thyroid if used during pregnancy - contraindicated
47
Q

management of thyroid storm

A
  • supportive therapy, treating the underlying disease process that may have precipitated the acute storm
  • propylthiouracil
  • iodides
  • propranolol
  • corticosteroids
  • bile acid sequestrants
48
Q

Management of thyrototoxicosis

A
  • Propylthiouracil in 1st trimester (lower risk of teratogenicity than methimazole)
    • methimazole can be given for the remainder of the pregnancy to avoid potential liver damage
  • subtotal thyroidectomy
  • RAI is contraindicated during pregnancy - crosses the placenta injuring fetal thyroid
49
Q

amiodarone effect on thyroid hormone

A
  • induced hypothyroidism via
    • inhibiting 5’deiodinase and TH synthesis
      • treat with levothyroxine
  • induced hyperthyroidism via
    • provides excess iodine increasing synthesis and release
      • treat with antithyroid drugs
    • autoimmune thryoiditis causing excess hormone release
      • treat with glucocorticoids

Pharmacology (19 decks)

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