Thyroid 3 - Hyper Meds
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Dose of Propylthiouracil (PTU)
- Initial: 300-600 mg po in 3-4 divided doses (Max 1200 mg/day)
- Maintenance: 50 - 300 mg po daily
Dose of methimazole (MMI, Tapazole, Northyx)
- Initial: 30 - 60 mg po in 3 divided doses (max 120 mg/day)
- Maintenance: 5 - 30 mg po daily
What are the indications for pharmacologic therapy with PTU or MMI? (Preferably MMI given the hepatotoxicity of PTU)
- > 40 yrs old
- Duration of disease < 6 months
- Small thyroid (< 50 grams)
- No Hx of relapse
- Duration of therapy 1 - 2 years or longer
If hyperthyroid relapse occurs after treatment with PTU or MMI (MMI preferred due to hepatotoxicity of PTU), what treatment is desirable as opposed to a second course of medication?
What is the MOA of PTU and MMI?
They are preferential substrates for thyroid peroxidase and thus block the conversion of MIT and DIT to T4 and T3. PTU also inhibits peripheral conversion of T4 to T3.
What are the brand names for MMI?
How long until hyperthyroid-symptoms diminish? How long until thyroid levels normalize?
- - 2 weeks until symptoms diminish
- - 4-8 weeks until levels normalize
- *BEGIN TAPERING TO MAINTENANCE DOSE AT THIS TIME (MONTHLY CHANGES)
How often should TSH levels be checked after initiation of thionamide therapy? Duration of frequent monitoring? Why?
Check thyroid function tests q 6-8 weeks for the first 4-6 months. Labs will lag.
For long term remission of hyperthyroidism to occur, how long do pts typically need to receive treatment? How often does this happen?
- 12 - 24 months
- Occurs in 40-50% of pts
How often should TSH be monitored in pts who are in hyperthyroidism remission?
Monitor every 6-12 months.
What are the predictors of treatment success for hyperthyroidism?
- 1. > 40 yrs of age
- 2. Low T4:T3 ratio (< 20)
- 3. Small thyroid (< 50 g)
- 4. Duration of disease ( < 6 months)
- 5. No Hx of relapse
- 6. Duration of therapy ≥ 1-2 years
If hyperthyroidism relapse occurs after initial treatment, what is preferred second course of antithyroid medication?
Radioactive iodine (RAI)
Why is MMI preferred over PTU?
PTU's adverse effect is a blackbox warning for hepatotoxicity
When is the only time PTU is considered the DOC for hyperthyroidism? Why?
- In expected/planned pregnancy and during the 1st trimester of an actual pregnancy.
- MMI associated with fetal anomalies.
- Keep maternal free thyroxine levels in upper 1/3 of normal to avoid fetal hypothyroidism.
What form of iodine is used in RAI therapy? What is its MOA?
- Sodium iodide 131.
- RAI disrupts hormone synthesis by incorporating into thyroid hormone and thyroglobulin.
On RAI, a transient (increase/decrease) in thyroid hormone levels will occur.
How many days after RAI can a patient be put on iodide treatment for hyperthyroidism?
If a patient is on hyperthyroidism medication and is to be switched to RAI, for how many days should the prior medication be held?
4 - 6 days
If a patient with hyperthyroidism is on RAI, and is to be switched to antithryoid medication, how soon can new treatment be initiated?
4 days after RAI
In the long-run, RAI treatment often returns a patient to normal thyroid function.
False. Over time, RAI therapy results in the destruction of the thyroid and most pts become hypothyroid.
What are the short-term adverse fx of RAI therapy?
Mild gland tenderness and dsyphagia.
________ is an absolute contraindication to RAI therapy.
What is iodide's place in therapy in the treatment of hyperthyroidism?
Adjunct therapy to prepare for surgery - 7 to 14 days prior to surgery.
What is the MOA of iodide solutions in the treatment of hyperthyroidism?
An acute "power-surge" of iodide briefly disables the release of thyroid hormone from the thyroid.
Large doses of iodide solution may worsen hyperthyroidism.
_________ is a contraindication to iodide solution therapy in the treatment of hyperthyroidism.
Toxic multinodular goiter
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