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Name a few causes of HYPOthyroidism
- Hashimoto's (70%)-enflamed goiter w/decreased function
- Surgical removal
Are all T4 drugs equal?
NO! Generics are not equivalent to trade names
When would T3 (liothyronine or Cytomel) medications be used?
in acute care (Myxedema coma)
How do thyroid hormone medications work?
- Produce same effects in the body as endogenous thyroid hormones.
- Also produce negative feedback loop to reduce further secretion of TSH and thyroid hormones.
______ is the drug of choice for thyroid replacement and suppression therapy because of it's longer half life.
Levothyroxine. It is metabolized in liver. T4 converted to T3 in body so Levothyroxine produces both hormones...
How long does it take for Levothyroxine to reach steady state?
- 6 weeks, very LONG half life.
- Hard to switch doses/brands (need to recheck levels 6-8weeks)
How is Levothyroxine excreted?
When is Levothryoxine contraindicated?
After an acute MI or thyrotoxicosis (pt has excessive levels w/increased HR, anxiety, & sweating)
Can you give Levothyroxine during pregnancy?
YES! It's category A. Replacement is advised for pregnant women.
Why might you have to increase the dose of Levothyroxine during pregnancy?
- Increased metabolic rate so may need higher dosing.
- Need frequent level checks, may require several dose changes. Check at 6-8weeks then again at 6M
TRUE or FALSE
Children with hypothyroidism don't need treatement
FALSE! Thyroid replacement is safe for the kiddos and they need it for cognitive development.
What happens if you don't treat hypothyroidism in pregnancy?
- Increases maternal health risk, still births, low birth weight & possible fetal brain development (baby's IQ dependent on adequate amount of thyroid hormone)
- Keep TSH at LOW NORMAL.
TRUE or FALSE
Thyroid replacement is excreted in breastmilk
TRUE but minimal excretion
TRUE or FALSE
Infertility and menstrual irregularity may improve with thyroid hormone replacement therapy.
Why shouldn't you give thyroid replacement medications to someone w/CAD?
Can increase workload of heart
Can thyroid replacement worsen osteoporosis?
YES, requires careful monitoring
Maria is depressed...what should be part of her work up?
Patients on levothyroxine need to watch for signs of thyrotoxicosis. What should they look for?
- Think HYPERTHYROIDISM
- Angina, increased BP, flushing, palpatations, increased HR, hyperthermia, anxiety, HA, insomnia, tremors.
Marian is overweight and wants you to increase her thyroid medication so she can drop a few lbs. Do you do it?
No! She could get Afib or decreased bone density. Tell Marian to get off the couch and eat a few less chips!
How do antacid and estrogens interact with Levothyroxine?
- Antacids DECREASE absorption
- Estrogens DECREASE response
- ...also interacts w/bile-acid sequestrants and iron salts
What happens if you take Levothyroxine with warfarin, digoxin, or beta blockers?
Levothyroxine may decrease the action of these medications
Should you start Levothyroxine treatment for a TSH of 12?
Yes, TSH greater than 10μIU/ml should be started on tx
Abby has a TSH of 7 and a goiter (and/or a positive anti-thyroid peroxidase antibodies), do you start Levothyroxine?
YES! TSH between 5-10μIU/ml w/a goiter or positive anti-thyroid peroxidase antibodies
TRUE or FALSE
Levothyroxine replacement therapy is only temporary
FALSE, it is lifelong!
You suspect your patient has hypothyroidism, when should you get an endocrine consult?
- Or complex patient who doesn't respond to therapy
How do you know the thyroid replacement therapy is effective?
Reduction of symptoms and normal TSH/Free T4
How should Abby take her thyroid replacement medication?
In the morning, on an empty stomach (there are many drug interactions!)
Rhonda is young and otherwise healthy except for her hypothyroidism. What dose should she be started at?
50-100 mcg daily
Barry is 51 yrs old and has known cardiac disease, what dose would you start his Levothyroxine at?
- 12.5-50 mcg daily
- for >50yr and/or known cardiac disease
You started Rhonda or Barry on Levothyroxine, when would you want a follow up to check their levels?
BEFORE you start treatment for hypothyroidism, what should you do?
STOP all medications with anti-thyroid effects (if possible)
At the 4 week check up (from starting Levothyroxine therapy), Abby's labs came back for euthyroid. When should you check her labs again?
Continue the dose and check TSH in 6weeks
At Barry's 4 week check up (after starting Levothyroxine), he's clinically euthyroid but his TSH is still high. What do you do?
Continue the current dose and recheck TSH in 4-8 weeks. If still euthyroid, continue dose and check TSH Q 6-12 M.
If TSH was still high at the 4-8week mark, refer to endocrinologist.
Kimberly was started on Levothyroxine therapy, and at the 4 week check up, she is still clinically hypothyroid and her TSH is still elevated. What do you do?
Increase her dose (by 25mcg/day for >50yr &/or known cardiac disease OR by 50mcg/day for young & healthy) then recheck in 4-8weeks
Kimberly was started on Levothyroxine, and had her dose increased at her 4 week check up, she's still hypothyroid at her next check up (4-8 weeks later). What do you do?
Increase in the same increment as before (by 25mcg/day for >50yr &/or known cardiac disease OR by 50mcg/day for young & healthy) and repeat TSH in another 4-8weeks.
If she's STILL hypothyroid then refer to endocrinologist.(aka, start dose, increase 2x and then refer!)
Sherry was started on Levothyroxine and had her dose increased at her 4 week check up. She is now euthyroid. What do you do?
Continue current dose and repeat TSH level every 6-12 M.
____ disease is the most common cause of Hyperthyroidism.
Can Hyperthyroidism be life threatening?
Beside Graves disease, what else can cause hyperthyroidism?
- Toxic Nodular Goiter
- Anterior Pituitary Disorders
- Plummer's Disease
- Amiodarone therapy
How long can it take to normalize hyperthyroidism?
Can you use medications and radiation therapy in hyperthyroidism?
Yes, goal is to destroy thyroid tissue
What type of drug is used to reduce symptoms while waiting for anti-thyroid drugs to work?
Beta blockers, decrease the HR associated with hyperthyroidism
Stephanie has Grave's disease, how long (at least) will she be on anti-thyroid drugs?
at least 1 yr for tx of Graves disease
What patient population responds best to radioactive iodine?
What is the oldest drug to treat hyperthyroidism and is safe in pregnancy?
Propylthiouracil (PTU) doesn't cross placenta!
What happens if you give PTU for hyperthyroidism to kids?
Issues with hepatotoxicity (do NOT use in children!)
Methimazole (Tapazole) has a ____ ___-___ but is pregnancy risk ___.
- longer half-life
- Pregnancy risk D (Crosses placenta)
How do PTU and Tapazole work in treating hyperthyroidism?
- Blocks the synthesis of thryoxine and triiodothyronine.
- Takes 6-12 M to see total reversal of ss
Do PTU or Tapazole treat underlying cause of hyperthyroidism?
NO, they don't treat underlying pathophysiology so there is a high relapse rate. (studies show less if tx 18-24 M)
We know PTU and Tapazole block thyroid synthesis, but how?!
(Also remember, doesn't effect what thyroid already made or what's in blood)
- Iodide is actively transported into the thyroid then oxidized to active form of Iodine.
- Iodine is component in making T3 and T4.
- Perioxidase enzyme aids this process
- (goal is to inhibit it=no T3 and T4 synthesis)
What are the major side effects of PTU or Tapazole (Methimazole)?
- Renal/Hepatic failure
drowsiness, HA, alopecia, skin rashes
What two medications do anti-thyroid medications (PTU, Methimazole) interact with?
Lithium and Warfarin
Merrill missed a dose of her anti-thyroid medication. Should she make it up?
NO, but remind her it is important not to miss doses!
Dietary sources of ____ should be REDUCED for a patient with hyperthyroidism.
- Iodine. they interfere with the action of drugs!
- Remind pt about iodized salt, seafood, dairy, etc.
Merrill has hyperthyroidism and is taking an anti-thyroid medication (PTU or Methimazole). She just came down with a cold and calls you to see if she can take an OTC medicine. What do you say?
NO, OTC cold medicines contain iodine. Pretty awful for Merrill...
What lab work should you obtain before starting an anti-thryoid medication like PTU or Methimazole?
- TSH & Free T4
- CBC (agranulocytosis is SE)
- Liver/renal panel (failure is SE)
When should you recheck labs after starting an anti-thyroid medication like PTU or Tapazole (Methimazole)?
1-2 M after starting drug