thyroid disease Flashcards
What drug class is levothyroxine (synthroid)
Thyroid hormone replacement (T4)
What is the MOA of levothyroxine (synthroid)
Replaces normal levels of T4 and T3 (T4 is converted into T3 in the periphery)
What are the indications for levothyroxine (synthroid)
Hypothyroidism. Also TSH suppression in select cases of thyroid nodules and thyroid cancer
How long does it take to reach a levothyroxine steady state
6-8 weeks
How is levothyroxine dosed
always in mcg (micrograms)
What is the half life of leothyroxine
~ 1 week
What are risks of having long term elevated T4
May accelerate cardiac disease and osteoporosis
In a patient with Addison’s and hypothyroidism, what is the appropriate pharmaceutical treatment
First replace cortisol, then thyroid. Not replacing cortisol first can be fatal
How does Thyroid USP (armor) compare to levothyroxine
It is porcine derived, and contains T3 and T4, along with some iodine and T1 and T2
How much is 1 grain of thyroid USP (armour)
60mg, which = 100mcg of synthroid
When should follow-up TSH testing be done
4-6 weeks, unless there is sweating anxiety, palpitations, increased heart rate, angina, etc
What is Liothyronine (Cytomel)
T3 thyroid replacement hormone.
What are the indications for liothyronine (cytomel)
For those intolerant or unresponsive to T4 replacement; myxedema coma; Wilson’s syndrome
What is the dosage of cytomel
25mcg = 100mcg of synthroid = 60mg Armour
Why are beta blockers used in hyperthyroid
because they block the adrenergic ssx like sweating palms, anxiety, etc
How is super saturated potassium iodine (SSKI) used in treatment of hyperthyroid
Supraphysiologic doses can be used to stun the thyroid, with effects lasting 2-3 weeks. helpful in thyroid storm
What drug class is Methimazole (Tapazole)
Thionamide
What are the indications for methimazole (tapazole)
Hyperthyroidism (Grave’s dis.) Can control hyperthyroidism until more definitive therapy (surgery or 131I therapy) is used
What is the MOA of methimazole (tapazole)
Inhibits transformation of inorganic iodine to organic iodine, therefore blocking the production of thyroxine. Also inhibits the coupling of iodotyrosine to form T3 and T4. Minimal effect of blocking the peripheral conversion of T4 to T3
How does methimazole compare to Propylthiouracil (PTU)
Propylthiouracil has much greater peripheral effect, methimazole has much greater central effect
What is the most feared side effect of methimazole and Propylthiouracil (PTU)
agranulocytosis
What category are methimazole and Propylthiouracil (PTU)
Category D (use it only if you have to)
How is radioactive iodine used
131 I is used for ablation of the thyroid in hyperthyroidism ( 123 I is used for radioactive uptake imaging)
How is hyperthyroidism managed in pregnancy
Methimazole is to be begun at the second trimester, with PTU still being used in the first trimester because PTU has more cases of hepatitis
What are the indications for Propylthiouracil
hyperthyroid from Graves or toxic goiter. Not for thyroid storm
What are the effects of propanolol in hyperthyroidism
Blockade of adrenergic symptoms of hyperthyroidism (i.e. tachycardia, anxiety). Emergent treatment of thyroid storm.
What category is radioactive iodine
category X
What are the outcomes of radioactive thyroid ablation
increased risk of parathyroid adenoma, no increase of thyroid cancer, temporary nausea and tenderness. may need to be on thyroid medications for life
