Endocrine- Thyroid

Question 1

2 pharmacological Treatments for Hyperthyroidism

Answer 1

Propylthiuracil (PTU)
Methimazole

They function by preventing the reduction of T4 to T3
T3- 3-4x more active

Question 2

How long do PTU and Methimazole take to work and why?

Answer 2

1-2 weeks, d/t stores of hormones in the thyroid gland

Question 3

More common Side effects of PTU and methimazole

Answer 3

-Formation of a goiter, d/t increase in TSH and hypertrophy of thyroid tissue

• Rash
• Arthralgia—common reason for d/c

Question 4

Rare side effects of PTU and methimazole

Answer 4

• Agranulocytosis— w/in 1st 90 days
• Hepatotoxicity
• Vasculitis

Question 5

Methimazole basic pharmocokinetics

Answer 5

• Longer half-life than PTU (1x daily dosing)
• More potent
• Less frequent serious side effects

Question 6

Propylthiouracil (PTU) basic pharmacokinetics

Answer 6

• Short half-life (3x daily dosing)
• Inhibits T4 conversion in periphery as well as thyroid
• Preferred in Pregnancy
• Preferred in Thyroid Storm d/t peripheral inhibition of T4 to T3 conversion

Question 7

How must PTU be given

Answer 7

Oral! No IV formulation, place NG for intra-op thyroid storm

Question 8

Surgical and other treatment for Hyperthyroidism

Answer 8

• Surgical Removal
• Radioactive Iodine- Thyroid takes up all the iodine (like Maggie with her snacks) and then the Beta rays are released into the thyroid tissue killing it.

Question 9

Pharmacologic Symptomatic treatment of Hyperthyroidism

Answer 9

• Beta Blockers
• Corticosteroids
• Iodide Salts

Question 10

Why are beta blockers used and which agent for thyroid storm?

Answer 10

Beta-Blockers

• Use esmolol for thyroid storm d/t onset and DOA
• used while waiting for thioamines (PTU) to work
• Block Hyperadrenergic effects (Tachy, Tremor, Nervousness)
• Block peripheral conversion of T4 to T3

Question 11

Why are Corticosteroids used in Hyperthyroidism?

Answer 11

• Symptomatic Treatment
• Block conversion of T4 to T3
• Supress thyroid receptor Ab and inflammation

Question 12

How do Iodide Salts treat hyperthyroidism

Answer 12

• Thyroid takes up all the Iodide and temporarily stops releasing thyroid hormone
• After all of it is taken up will have large release of T3/T4
• TEMPORARY

Question 13

Pharmacological Treatment for Hypothyroidism

Answer 13

• Levothyroxine (T4) (Better to have T4 and let body convert to T3)
• Cytomel (T3)

Question 14

Levothroxine Pharmacokinetics (what is it, half-life, strength, side effects, route, labs to monitor)

Answer 14

• Drug of Choice
• Synthesized T4
• Half-life 7 days (1x daily dosing, can miss a dose)
• Wide range of available Strengths
• Monitor TSH and Free T4
• Side Effects- Allergic Rash, secondary to dye
• PO route preferred but can be IV emergent

Question 15

When would Cytomel use be beneficial?

Answer 15

Life threatening hypothyroidism (Myxedema Coma)

–Half Life 1 day

Question 16

Levothyroxine (Synthroid) Drug interactions

Answer 16

Increase Levothyroxine Metabolism
— Phenobarb, Phenytoin, rifampin, carbamazapine

Decerases T4 to T3 conversion
— PTU, B-Blockers, Glucocorticoids, Amiodarone

Decreases Absorption from gut
— Cholestyramine, FeSO4, Al(OH)3, Sucrfate

Increases THyroid binding Globulin
— Pregnancy, estrogen

Question 17

Drugs that can alter thyroid status (none of the ones we already talked about)

Answer 17

Amiodarone

• • Structurally resembles thyroid hormone and contains large amounts of iodine
• • Can result in HYPO or HYPER thyroidism

Lithium

• • Concentrated in Thyroid by body
• -Body thinks it is iodide
• • inhibits thyroid synthesis leading to HYPO

Reglan
–Increased TSH production and release