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Flashcards in Thyroid Deck (27):
1

What are the two major thyroid hormones?

Thyroxine (T4)
Tri-iodothyronine (T3)

2

How much T3 is produced in the thyroid itself?

20%

3

Where does the majority of T3 come from

80% comes from peripheral breakdown of T4

4

How many half-lives do thyroid hormones have in steady state?

4-5

5

What does the thyroid do?

Regulates hormone production
This is done via the hypothalamic pituitary thyroid axis

6

How do we get thyroid hormone?

TSH secreted by anterior pituitary
Or..
T4 is converted to T3 outside the thyroid

7

What kind of disorder is primary hypothyroidism

Disorders of the thyroid gland
Aka: Hashimoto's thyroiditis

8

What kind of disorder is secondary hypothyroidism

Pituitary or hypothalamic dosorders

9

Sx of hypothyroidism

Weight gain
Depression*
*When working a pt up for depression checking for hypothyroidism is ESSENTIAL*

10

Diagnosing hypothyroidism

Check TSH and a free T4 (or total but free is better)

11

Levels of hormones in subclinical hypothyroidism

Increased TSH but normal T4

12

Levels of hormones in hypothyroidism

Elevated TSH
Low T4

13

Drug of choice for hypothyroidism

Levothyroxine

14

Levothyroxine

Synthetic T4
Long half life
Once daily dosing
IV dosing at 50% of oral dose
Dosing in mcg!

15

Little used hypothyroidism tx

Desiccated beef/pork thyroid gland (Armour -> mg dosing)*
*Obsolete and potential for allergy*
T3 and T4 mixtures (Liotrix) -> expensive, no real theraputic rationale

16

Levothyroxine dosing

Dosed one daily in AM on EMPTY STOMACH
Typical dose = 100-112 mcg/day

17

Under what circumstances do we used alternative dosing of levothyroxine

Lower initial dosing for the elderly and pts w/ CV disease
Pregnancy usually requires higher dosing

18

Hyperthyroidism sx

Nervousness
Anxiety
Palpitations
Heat intolerance
Finger tremor
Weight loss (cardinal sign)

19

Main cause of hyperthyroidism

Grave's disease

20

Classic triad of Grave's disease

Hyperthyroidism
Opthalmopathy (bugged out eyes)
Dermopathy (pretibial myxedema)

21

Hormone levels in hyperthyroidism (dx)

Decreased TSH
Increased T4

22

Hyperthyroidism tx

Antithyroid meds

23

Anti-thyroid meds

Propylthiouracil (PTU)
Methimazole

24

PTU

Inhibits conversion of T4 to T3
TID dosing
Evaluate pts 3 months after D/Cing to check for recurrence

25

Methimazole

10xs more potent than PTU
Blocks oxidation of iodine in thyroid
No effect on T3 or T4

26

Dosing of methimazole for mild, moderate, severe, and maintenance is how many times per day

3!
TID

27

SE of anti-thyroid meds

Agranulocytosis
Aplastic anemia
Thrombocytopenia