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59 Cards in this Set
- Front
- Back
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When are newborns screened for thyroid hormones?
Why can't you screen them after mom started nursing the baby? |
within 2 days.
nursing may mast hypothyroidism from mother's milk |
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What happens when treatment with T4 begins after several years of neonatal cretinim?
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can still increase growth but may leave some mental deficits.
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List 3 treatment for hyperthyroidism.
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1. antithyroid drugs
2. radioactive iodine 3. thyrodectomy |
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Mechanism of action of thiocyanate and perchlorate.
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block iodine trap in the thyroid follicular cells.
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Mechanism of action of PTU.
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- block peroxidation
- block organification - block coupling (MIT, DIT formation) - block 5' monodeiodinase which convert T4 to T3 |
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Mechanism of action of MMI.
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- block peroxidation
- block organification - block coupling (MIT, DIT formation) |
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What is the function of 5' monodeiodinase and 5 monodeiodinase?
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5' monodeiodinase (outer ring): convert T4 to Tx
5 monodeiodinase (inner ring): convert T4 to rT3 |
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Name some blockers of 5' monodeiodinase.
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- ipodate
- glucocorticoids - amiodarone - PTU |
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If a patient discontinued taking 0.1mg Levothroid for awhile and wants to restart the treatment. What dose should you start with?
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start with 1/2 of maintanence dose. In this case, should start at 0.05mg then titrate up.
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A patient is taking 0.1mg Levothroid regularly. He forgot to take the drug for one day. How would you respond?
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Continue taking it the next day at the same dose since T4 has a long half life, missing one day is not a big deal.
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What are some disadvanges of taking Liothronine (T3)?
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- difficult for lab monitor
- short half life - should not be used in patients with cardiac disease |
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Thyroid hormone absorption from bowel is enhanced by ____ and inhibited by _____.
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Thyroid hormone absorption from bowel is enhanced by fasting and hypothyroidism and inhibited in old people and people with malabsorptive diseases.
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Who require less T4?
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men and elderly women
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Who require more T4?
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children
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Effect of the following on thyroxine dosing.
- estrogen |
increase TBG -> need higher dose
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Effect of the following on thyroxine dosing.
- androgen |
decrease TBG -> need lower dose
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Effect of the following on thyroxine dosing.
- cholestyramine |
inhibit bile absorption, enhance LDL clearance -> need to take T4 12 hrs after
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T/F: Elderly with long standing hypothyroidism are very sensitive to cardiac effects of T4.
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T.
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Mechanism of action of thyroid replacement drugs.
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- free hormone diffuse into cell and bind to TR in the nucleus: homodimers or heterodimers (TR+retinoic X receptor).
- dimers dissociate co-repressor and recruits co-activators of gene transcription -> up regulate gene expression - also down regulate gene expression by TR-independent mechanism |
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What are some indications of incomplete thyroid hormone replacement therapy in hypothyroid patient?
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- persistent eyelid ptosis
- hyperkeratosis of elbows - slight delay in relaxation phase of deep tendon reflexes |
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Name some drugs that dissociate T3 and T4 from TBG with transient hyperthyroxinemia.
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- NSAIDs: salicylates, fenclofenac, mefenamic acid
- furosemide |
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Higher or lower dose of warfarin required?
- patient with hyperthyroidism |
low
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Higher or lower dose of warfarin required?
- patient with hypothyroidism |
higher
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Higher or lower dose of digoxin?
- patients with hyperthyroidism |
higher
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Higher or lower dose of digoxin?
- patients with hypothyroidism |
lower
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How to treat and monitor primary hypothyroidism?
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- treat with hormone replacement
- monitor with TSH level |
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How to treat and monitor central hypothyroidism?
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- T4 and cortisol (may also have adrenal insufficiency)
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What may happen when you give T4 only to patients with central hypothyroid?
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adrenal crisis
- these patient may also have adrenal insufficiency - T4 increases rate of metabolism of steroids |
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Untreated hypothyroidism may lead to what medical emergency?
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myxedema coma
- treat with IV T4 - may need to also give steroids |
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What is the most common cause of hyperthyroidism in areas where iodine intake in adequate?
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Graves disease
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T/F: Graves disease exacerbates during pregnancy but improves postpartum.
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F.
Graves disease exacerbates during pregnancy but improves postpartum. |
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What types of mangement are there for hyperthyroidism?
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- medicine (thionamide)
- radioactive idodine (RAI) - destructive surgery with subtotal thyroidectomy |
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What is the drug of choice for post menopausal women who develop hyperthyroidism?
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radioiodine
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Compare PTU and MMI in the following aspects:
- peak serum level - serum half life - serum protein binding - cross placenta or not - potency - duration of action |
PTU
- 60 min to reach peak serum level - half life: 1-2 hrs - serum protein binding: 75% - do not cross placenta - low potency - duration of action: 12-24 hrs MMI - 60-120 min to reach peak serum level - half life: 6-8 hrs - no serum protein binding - cross placenta - high potency - duration of action: >24 hrs |
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Mechanism of action of thionamides.
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- block TPO-mediated oxification
- block organification (iodination) - block coupling - PTU also block 5' monodeiodinase at low dose, reversible at high dose, irreversible high [iodine] will counteract the irreversible inhibition of hormone biosynthesis |
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Mechanism of thionamides in treating Graves disease.
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- decrease TSHR antibody
- increase activated T cell - increase levels of cytotoxic-suppressor cells to normal |
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PTU or MMI?
- irreversible inhibition of TPO |
MMI
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PTU or MMI?
- preferred in lactating and pregnant patients |
PTU
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PTU or MMI?
- DOC in children |
MMI
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PTU or MMI?
- preferred for severe hyperthyroidism |
PTU
- bacause of peripheral inhibition of 5' monodeiodinase |
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Common minor side effects of thionamides.
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- pruritis
- urticaria - urthalgia other minor side effects - abnormal taste - GI upset - hypoglycemia |
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DOC for treating hyperthyroidism in elderly.
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RAI
- medication may cause serious side effects such as agranulocytosis (MMI), aplastic anemia, thrombocytopenia, hepatitis (PTU), jaundice(MMI), and lupus like syndrome. |
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How to treat mild hyperthyroidism?
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- beta-blocker prior ro RAI/surgery
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What do you treat this with?
- hyperthyroidism with severe T3 toxicosis or cardiac disease |
corticosteroids
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Why should you not use iodine or ipodate to treat severe T3 toxicosis?
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it may cause iodine induced hyperthyroidism (Jod-Basedow phenomenon)
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What do you treat this with?
- thyroiditis |
- NSAIDs ot propranolol
* may remit spontaneousely within several months |
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What is the most common of hyperthyroidism in elderly (age > 60)?
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toxic multinodular goiter
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Name some iodide trap inhibitors.
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- thyiocyanate (SCN-)
- perchlorate (ClO4), pertechnetate (TcO4) * these are present in vegetables like cabbage * perchlorate may cause aplastic anemia |
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What are some uses of high dose iodide?
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- preparation for thyroidectomy
- with thionamide as early treatment for severe thyrotoxicosis - after RAI therapy to protect the thyroid from RAI fallout - in patients who are allergic to thionamides |
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What are some effects of high dose iodide on thyroid function?
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- inhibit iodide organification
- inhibit hormone release - decrease size and vascularity of a hyperplastic gland * max effect at day 10-15 |
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I129 or I 131?
- used for diagnosis |
I129
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I129 or I 131?
- used for treatment |
I131
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What are some restriction on radioactive iodide use?
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- not used in women of child bearing age: it will cross placenta and is secreted in breast milk
- requires subsequent continuous replacement therapy with T4 |
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What is the preferred drug for treating thyroid storm?
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esmolol
- rapid onset - short half life |
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How is beta blockers useful in hyperthyroidism?
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- symptomatic relief of palpitations and tremors
- inhibit peripheral conversion of T4 to T3 - avoid masking hypoglycemia in patients with DM |
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How is corticosteroids useful in hyperthyroidism?
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- adjunctive to control accelerated hyperthyroidism
- management of painful subacute thyroiditis - inhibit 5' deiodinase * limit use less than 2 wks |
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What is Wolff-Chaikoff effect?
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large iodide load given to euthyroid individual lead to thyroid gland suppression.
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What effects does lithium have on thyroid function?
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- inhibit hormone release
- can be as adjunctives to thionamides and steroids for rapid control of thyrotoxicosis |
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What effects does amiodarone have on thyroid function?
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- structually resembles thyroid hormone and contains iodine -> cause wolff-chaikoff effect
- cause hyperthyroidism - inhibit 5' monodeiodinase |
