Hypothyroid

Question 1

What is the function of the thyroid gland

Answer 1

Secrete thyroid hormones (T3/T4) to regulate metabolism

Secrete calcitonin to regulate calcium (decrease)

Question 2

What is thyroglobulin

Answer 2

Protein that synthesizes and stores T3 and T4

Question 3

What is the HPA axis overview

Answer 3

Hypothalamus releases TRH to the ant pituitary
Ant pit releases TSH to the thyroid
TSH tells the thyroid to make T3 and T4
Unused T3/T4 in the blood go to the hypothalamus and anterior pituitary with negative feedback
Hypothalamus and Ant pit stop stimulating T3/T4 release

Question 4

What are the two overall manifestations of hypothyroidism

Answer 4

Generalized slowing of metabolism

Accumulation of polysaccharides in the matrix

Question 5

What are general slow metabolic Sx of hypothyroidism

Answer 5

Fatigue
cold intolerance 
weight gain (mild)
cognitive dysfunction 
constipation 
slow movement/speech
delayed relaxation of DTR 
Bradycardia

Question 6

What are Sx of polysaccharide accumulation in hypothyroidism

Answer 6

Dry skin 
hoarseness
edema
coarse skin 
puffy face 
loss of eyebrows 
periorbital edema 
tongue enlargement

Question 7

Other (not as frequent) Sx of hypothyroidism are

Answer 7

decreased hearing
myalgias
depression 
menstrual changes 
pubertal delay 
diastolic HTN 
pleural/pericardial effusions 
ascites 
galactorrhea

Question 8

Some PE findings for hypothyroidism include

Answer 8

carpal tunnel (2/2 edema causing nerve compression)
Hypoactive bowel sounds
Dyspnea
Hypertension Sx of vitiligo or alopecia

Question 9

Classic hypothyroidism labs show

Answer 9

High TSH
Low free T4
May want to get BMP (Na and Cr), Lipids (HLD), and drug levels (hard to metabolize drugs)

Question 10

How can you tell the difference between primary and subclinical hypothyroidism

Answer 10

Primary: high TSH, low T4
Subclinical: high TSH, normal T4

Question 11

What are the anti-thyroid antibodies

Answer 11

Anti-TPO: high in graves and hashimotos
Anti Tg: high in graves and hashimotos
TSH recetor (TSI): high in GRAVES (specific)

Question 12

MCC of hypothyroidism in U.S. is

Answer 12

Hashimotos (autoimmune thyroiditis)
In the world: iodine deficiency
Also: iatrogenic, meds, transient (pregnancy), infiltrative, congenital

Question 13

Do you screen everyone for hypothyroidism?

Answer 13

USPSTF says no (no EBM on effectiveness)

But in real practice, you will

Question 14

Who is at increased risk for hypothyroidism (and therefor should likely be screened)

Answer 14

Goiter 
Hx AI disease 
Hx radioactive iodine therapy 
Hx head/neck radiation 
FHx thyroid disease 
Meds that impair thyroid fxn (lithium, amiodarone)

Question 15

Once hypothyroidism has been diagnosed, how do you treat it

Answer 15

Synthetic thyroxine (T4) replacement to achieve and maintain euthyroid state; 80% absorption, 1 week half life
Brand: Levothyroxine
Generic: levothyroid, levoxyl, synthyroid

Question 16

Is brand better than genetic?

Answer 16

Endocrinologists think so bc with brand you get the same formulation every time so you better achieve and maintain euthyroid
With generic you get different formulations making it harder to maintain

Question 17

How do you dose Levothyroxine

Answer 17

average dose: 1.6 mcg/kg/day
Elderly: 25-50 mcg/day, titrate up
Hx CHD: MAX 25 mcg/day, titrate up

Question 18

Goals of hypothyroid Tx are

Answer 18

Symptom relief
Normalize TSH secretion
Decrease goiter (if applicable)

Question 19

How do you manage hypothyroid therapy

Answer 19

Monitor labs q6 weeks until TSH is normal

avoid OVER replacement and sending into hyperthyroid

Question 20

Weird hypothyroid drug combos are

Answer 20

T3/T4 combo (cytomel): T3 absorption is highly variable and has a short half life to it is hard to get consistent levels in the system
Dessicated thyroid extract (Armour thyroid): extracted form pigs, for patients who want “natural” drug. has T3 and T4. Endocrinologists hate it

Question 21

Do meds interact with levothyroxine

Answer 21

Yes, many!
Ferrous sulfate, PPI
just take them at a different time during the day

Question 22

What is subclinical hypothyroid

Answer 22

Associated with CVD, NAFLD, Neuropsych, and reproductive d/o
1/2 progress to primary hypothyroidism

Question 23

How do you treat subclinical hypothyroidism

Answer 23

If TSH >10: Give supplemental T4

If TSH 5-10: only treat if symptomatic! what is their clinical presentation?