Thyroid and Antithryoid Flashcards
drugs that are thyroid preps
Levothyroxine (T4)
Liothyronine (T3)
Liotrix (T3, T4)
Adjunct therapy agents
propranolol
diltiazem
barbituates
bile acide sequetrants
Thyroid hormone synthesis:
iodide uptake into thyroid gland by the 1
2 mediated oxidation of iodide to iodine
- sodium/iodide symporter
2. peroxidase
when is transcription repressed
absence of thyroid hormone; unbound T3 receptor
what converts T4 to T3
5’-deiodinase
when is thyroid synthesis inhibited and when is it promotes
High = inhibit NIS, iodination, hormone release
Low = stimulate TSH release and T3 production
what is the goal in treating hypothyroidism
increase [T4] in blood
normalize TSH
alleviate sx
what is the tx of choice for hypothyroidism
Levothyroxine
- activation of T3 receptors
- 7 day T1/2
why treating hypothyroidism what is a special consdieration that needs to be addressed?
Coronary artery disease
- in elderly there is often underlying CAD. Thyroid hormone is protective. Tx. must be done carefully not to provoke arrhythmias, angina, or MI
In graves disease autoantibodies stimulate TSH receptors and increase production of T3 and T4; would you expect TSH levels to be high or low
low
how would you treat hyperthryoidism
methimazole
propylthiouracil
(thioamides)
MOA of thioamides
inhibit peroxidase rxn, iodine organification, and coupling of iodotyrosines
what is a consideration for the use of thioamides
low levels cross placental barrier - risk of fetal hypothyroidism
which thioamide would be preferred if femaile is in 1st trimester of pregnancy? why?
Propylthiouracil - more bound to plasma proteins
which thioamide is used for thyroid storm due to rapid absorption
propylthiouracil
which thioamide has a black box warning for severe hepatitis
propylthiouracil
what does the antithyroid agents potatssium iodide and lugol’s solution due to iodide stores?
increases intraglandular iodide stores thus delaying onset of thioamide therapy
why are iodides often used in combo with other agents
normally only inhibit for 2-8 weeks
- escape inhibition due to decrease in sodium/iodide transporter expression
withdrawal from iodides will produce ___
thyrotoxicosis
what drugs are useful for thyroid storms
Propylthiouracil
Iodides
Adjuncts - propranolol, atenolol, metoprolol
what drugs can be useful for preoperative preparation for surgery due to its impact on hyperplastic glands - decreases vascularity, size and fragility
Iodides - potassium iodide and Lugol’s solution
adverse effects of iodides
Cold sx - HA, sneezing, cough
MOA of radioactive iodines in tx hyperthyroidism
beta rays destroy parenchymal cells f thyroid
gama rays can be used in detecting [RAI] remaining in thyroid glands
why when treating hyperthyroidism with radioactive iodine do you often end up having to treat hypothyroidism
complete ablation can occur
After radioactive iodine tx what should be used to control hyperthyroidism while waiting for effect
beta blockers
iodide
or antithyroid drug
what is radioactive iodine therapy contraindicated for
pregnancy - concentrate in fetal thyroid
what are the anion inhibitors in treating hyperthyroidism
perchlorate
pertechnetate
thiocyanate
MOA of anion inhibitors
inhibit energy dependent uptake of iodide into the thryoid cell that is mediated by the sodium/iodide transporter
Effects of anion inhibitors can be overcome by what?
large doses of iodide
what type of hyperthyroidism do anion inhibitors treat
iodide-induced hyperthyroidism
adverse effect of perchlorate (anion inhibitor)
aplastic anemai
what is the major clinical use of propranolol in adjunct therapy
control tachycardia, HTN, and A fib
also inhibits conversion of T4 to T3
what adjunct can control tachycardia in asthmatics
diltiazem
what adjunct increase T4 metabolism
barbituates
what adjunct increases biliary T4 excretion
bile acid sequestrants
which drug for hyperthyroidism can cause rash, nausea, GI distress, agranulocytosis, altered taste and smel
Methimazole (taste/smell in particular)
propylthiouracil (severe hepatitis too_
what hyperthyroidism drugs can cause a metallic taste, sore gums and teeth, skin lesions, hypersensitivity, angioedema, laryngeal edema, goiter if taken during pregnancy
Potassium iodide
Lugol’s solution
