L34- Thyroid and Antithyroid Drugs (hyperthyroid)

Question 1

describe the management hierarchy for hyperthyroidism

Answer 1

1) pharmacotherapy
2) radioactive iodine (RAI) destruction of thyroid
3) surgical thyroidectomy

Question 2

list the pharmacological agents for hyperthyroidism

Answer 2

• thioamides
• iodides
• β-blockers
• glucocorticoids
• bile acid sequestrants

Question 3

Thioamides:

• (1) agents
• (2) MOA

Answer 3

1- methimazole, PTU (propylthiouracil)

2- inhibits thyroid peroxidase enzyme –> prevents iodide oxidation to iodine (+ –> interferes with iodination of tyrosyl groups on thyroglobulin –> inhibits coupling of iodotyrosyl residues –> inhibits TH formation)

Question 4

Thioamide:

• (1) is preferred agent because of (2) and except for in (3) situations
• (3) drug has (4) as additional MOA

Answer 4

1- methimazole > propylthiouracil (PTU)

2- less toxic (liver injury), longer 1/2 life and duration (once daily)

3- (PTU) severe hyperthyroid, thyroid storms, 1st trimester

4- inhibits peripheral deiodination (T4 –> T3)

Question 5

list the therapeutic uses of Thioamides

Answer 5

• definitive Tx for hyperthyroidism
• conjunction w/ radioative iodine (quickens recovery)
• control hyperthyroid in preparation for surgery

Question 6

describe the role and regimen of iodides for hyperthyroidism

Answer 6

Iodides inhibit hormone release via thyroglobulin proteolysis inhibition and transient iodine organification inhibition

-NOT used alone b/c thyroid escapes iodide block in 2-8wks

Question 7

list the clinical applications of iodides

Answer 7

• Thyroid Storm: rapid improvement of Sxs
• preop for surgery –> dec thyroid size, vascularity of hyperplastic thyroids
• radiation emergencies involving release of radioactive iodine isotropes

Question 8

iodides AEs

Answer 8

(uncommon)
-precipitates hyperthyroidism (Jod-Basedow phenomenon) or hypothyroidism (no escape from Wolff-Chaikoff)

• delays onset of thioamide therapy – prevents use of radioactive iodine therapy for several weeks
• fetal goiter if used in pregnancy

Question 9

describe the use of β-blockers in hyperthyroidism

Answer 9

• alleviate the SNS / catecholamine Sxs precipitated by TH inc sensitivity to SNS
• Propanolol inhibits T4 –> T3
• CCBs to control tachycardia if β-blockers are contraindicated

Question 10

describe the use of glucocorticoids in hyperthyroidism

Answer 10

• inhibits peripheral T4 –> T3
• promotes vasomotor stability
• treats possible associated adrenal insufficiency Sxs

Manages Grave’s ophthalmopathy and dermopathy

Question 11

describe the use of bile acid sequestrants in hyperthyroidism

Answer 11

binds to TH metabolites to inhibit enterohepatic cycling of TH

Question 12

_____ is generally the preferred hyperthyroidism Tx

Answer 12

RAI- radioactive iodine (I-131)

-destroy thyroid parenchyma

Question 13

list RAI AEs

Answer 13

• hypothyroidism
• radiation thyroiditis
• exacerbates Grave’s ophthalmopathy

-destroys fetal thyroid in pregnancy

Question 14

Thyroid storms are triggered by….

Answer 14

infection
trauma
surgery
physical illness
severe emotional distress

Question 15

thyroid storm management

Answer 15

• supportive therapy
• treat underlying disease process / trigger

-PTU (propylthiouracil), iodides, propanolol, corticosteroids, bile acid seqesterants

Question 16

Amiodarone induced thyrotoxicosis 1:

• (1) definition
• (2) lab features
• (3) Tx

Answer 16

1- inc TH synthesis

2- low TSH, elevated T3/T4

3- antithyroid drugs

Question 17

Amiodarone induced thyrotoxicosis 2:

• (1) definition
• (2) lab features
• (3) Tx

Answer 17

1- destructive thyroiditis

2- low TSH, elevated T3/T4

3- glucocorticoids