Thyroid Disease

Question 1

T/F: thyroid levels should always be on differential for cognitive changes?

Answer 1

True

Question 2

What medications can affect the thyroid?

Answer 2

Amiodarone, Lithium

Question 3

What is the normal level of TSH?

Answer 3

TSH 0.4-0.6
*subclinical hypothyroidism involves slightly elevated TSH with no to minimal clinical symptoms

Question 4

Which is the active form of thyroid hormone?

Answer 4

T3, Levothyroxine is T4 so it must be converted to T3
*selenium deficiency can cause less conversion of T4 to T3

Question 5

T/F: The thyroid releases 100% of T4 and only 20% T3, the other 80% of T3 needs peripheral conversion.

Answer 5

True

Question 6

T/F: T4 has more plasma binding than T3.

Answer 6

True

Question 7

What is the conversion of levothyroxine to desiccated thyroid (Armour thyroid)?

Answer 7

Since desiccate thyroid is both t3 and t4, 60 mg of armour is approximately 100mcg of levo

Question 8

If needing to inc dose of levo, what should be assessed?

Answer 8

Adherence
Potential for binding interactions (mag, zinc, iron, ca, cholestryamine, etc)
Timing

Question 9

What are the meds used for HYPERthyroidism?

Answer 9

Methimazole: inhibits thyroid synthesis by interfering with oxidation of iodine, inhibition of peroxidase enzyme
Propylthiouracil (PTU): not first line, multiple dosing, BB warning for liver toxicity

Question 10

Why is T4 preferred over T3?

Answer 10

More stable, longer half-life, less clinical impact on missed doses, less risk for thyrotoxicosis

Question 11

T/F: acute illness can decrease protein binding of levo

Answer 11

True, thus causing more free drug activity

Question 12

What can increase the plasma binding of levo? Decrease?

Answer 12

Estrogen, estrogen agonist/antagonist, methadone, F-FU, liver disease, HIV

Corticosteroids, androgens, furosemide, salicylates, AEDs (ie phenytoin), acute illness

Question 13

What is considered OVERT and SUBCLINICAL hypothyroidism?

Answer 13

Overt: TSH >10 (Normal 0.1-4), dec T4 (normal: 0.7-1.9)
Subclinical: TSH <10, normal T4

Question 14

Do you have to treat subclinical hypothyroidism?

Answer 14

NO you dont but if patient symptomatic, it is recommended. Especially look for mental status changes.

Question 15

What level do you treat an elderly patient to for hypothyroidism?

Answer 15

If overt, treat to normal levels
If subclinical, treat to symptom resolution