Hypothyroidism

Question 1

Who do you treat hypothyroidism in?

Answer 1

Overt hypothyroidism
Subclinical hypothyroidism if the TSH is >10.0 mIU/L
Pregnant women/planning to get pregnant if TSH >2.5 mIU/L and have a positive TPO antibody

Question 2

Consider treatment in…

Answer 2

Subclinical TSH if TSH 4.5-10.0 mIU/L and are symptomatic, have a positive TPO antibody, CAD/CHF or risk factors

Pregnant/planning to be pregnant but not hypothyroid and

TSH 2.5-ULN in 1st trimester/planning
TSH 3.0-ULN in 2nd trimester
TSH 3.5-ULN in 3rd trimester

Question 3

Treatment goals for hypothyroidism

Answer 3

Get patient biochemcially euthyroid, symptomatic treatment, avoid oversupplementation (especially in elderly patients)

Question 4

Treatment options for hypothyroidism

Answer 4

Desiccated thyroid
Liothyronine
LEVOTHYROXINE

Question 5

Dessicated thyroid drug information

Answer 5

Thyroxine and triiodothyronine
Porcine origin
Proof of efficacy doesn’t exist so we don’t really use this anymore
For patients looking for an “all natural” solution

Question 6

Liothyronine drug information

Answer 6

Synthetic T3

Used in life-threatening hypothyroidism (injectable form)

Question 7

Levothyroxine drug information

Answer 7

T4 analog
Available IV and PO (IV is 50-75% of the PO dose)
Best medication to use in hypothyroidism

Question 8

Levothyroxine drug dosing for a normal, otherwise healthy <65 years old

Answer 8

1.6 mcg/kg/day (dosed by IBW)

Question 9

Levothyroxine drug dosing for an otherwise healthy ≥65 years old

Answer 9

50 mcg/day (but can be a lower dose in frail elderly patients)

Question 10

Levothyroxine drug dosing for known CAD

Answer 10

12.5-25 mcg/day

Question 11

Levothyroxine dosing for pregnancy

Answer 11

30% dose increase

Question 12

Levothyroxine dosing for severely obese patients (BMI >40 kg/m^2)

Answer 12

May require higher replacement doses but should still dose with IBW

Question 13

Levothyroxine dosing for autoimmune gastritis

Answer 13

May require higher replacement doses

Question 14

Levothyroxine treatment considerations

Answer 14

Keep patient on same brand!
IBW to calculate replacement dose
Levothyroxine is a narrow TI drug
TSH draw 4-6 weeks after switching brands

Question 15

Switching from levothyroxine to liothyronine

Answer 15

Divide levothyroxine dose by 4

Question 16

Switching from levothyroxine to desiccated thyroid

Answer 16

100 mcg= 1 grain

Question 17

Levothyroxine counseling

Answer 17

Only take with water and no other meds
Take 60 minutes before breakfast or at least 3 hours after evening meal (remain consistent!)
If they miss a dose, take it as soon as they remember but can double up doses if it’s close to the next time they need to take it

Question 18

Levothyroxine treatment expectations

Answer 18

Some weight loss, may take up to 6 weeks to see effect, lifelong therapy, decreased risk of cardiac and metabolic diseases

Question 19

Levothyroxine ADEs

Answer 19

Transient alopecia (but reverses itself), allergic reactions to the excipients, iatrogenic thyrotoxicosis

Question 20

Levothyroxine drug interactions

Answer 20

Metal cations (separate administration to either 4 hours before or after levo administration)

BAS, sucralfate, SPS

PPIs, H2RAs, orlistat

Estrogens, androgens, raloxifene

Sertraline, phenobarbital, phenytoin, quetiapine

Question 21

Levothyroxine treatment algorithm

Answer 21

1. Start with appropriate initial dose
2. Check TSH in 4-6 weeks and see if it’s WNL
   3a. If it’s not, titrate dose up or down by 12.5-25 mcg/day
   3b. If it is, check TSH again in 4-6 months, then at least yearly if there’s reason to suspect absorption or change in metabolism