Studied by 40 people
based on Khan SG
This structure is what hormone?
T4
What is the brand name of Liothyronine?
Cytomel
What is the brand name of Levothyroxine?
SYNTHROID, levoxyl
What is the brand name of Propylthiouracil?
PTU
What is the brand name of Methimazole?
Tapazole
What steps of thyroid hormone synthesis are inhibited by thioamides?
organification and coupling
What is organification?
Iodination of tyrosine residues within TG
What is coupling?
When the tyrosine molecules are joined together
Thyroid hormones use what kind of receptors?
a. nuclear
b. cytoplasmic
c. membrane
a
Why does T3 have a greater affinity for T4 receptors?
because it doesn’t have as much steric hinderance as T4 (The 5’ iodine on T4 causes more steric hinderance and T3 doesn’t have it.)
What enzyme converts T4 to T3?
5’ deiodinase
Which ring with be deiodinated when T4 is converted to T3?
a. outer ring
b. inner ring
c. neither
a
What is the mechanism that causes Hashimoto’s disease?
autoimmune destruction of the thyroid (selective destruction of thyroid, antibodies against TPO, TG, and TSH receptors)
What is the mechanism that causes Grave’s disease?
autoimmune disease where B lymphocytes secrete a TSH receptor stimulating antibody (binds like TSH, acts like TSH, and lasts longer)
What 3 drugs can be used for hypothyroidism?
thyroid desccated
liothyronine
levothyroxine
Answer the following characteristics of Levothyroxine:
It’s a synthetic form of what?
Is it the drug of choice?
What’s it’s half-life? long or short?
synthetic form of T4
drug of choice!!!!
long half-life
Levothyroxine interacts with what drugs to DECREASE ABSORPTION?
antacids
bile acid sequesterants
iron salts
sucralfate
sevelamer
multivitamins
Levothyroxine interacts with what drug and that enhances its effect?
warfarin
Levothyroxine interactions with what drugs that cause an increase in T4 metabolism?
CYP- 450 inducers (phenytoin, rifampin)
What are the boxed warnings of levothyroxine?
Must NOT be used to treat obesity/ for weight loss
in euthyroid individuals
high doses can cause life-threatening conditions with anorectic drugs (appetite suppressants)
Lower doses of levothyroxine must be used in patients with ______.
CAD
Drug induced hypothyroidism can be caused by lithium. How?
Lithium is concentrated in the thyroid and inhibits hormone release
Drug induced hypothyroidism can be caused by Amiodarone. How?
decreases T4 to T3 conversion also inhibits thyroid synthesis and release
What are the 3 treatment options for hyperthyroidism?
anti-thyroid drugs
surgery
radiation tx
How does radioactive iodine work in hyperthyroidism?
destroys the thyroid tissue using beta radiation
What are the advantages of using radioactive iodine?
easy to administer, less expensive, painless, effective
What will be the initial problem of radioactive iodine? What will be the ultimate effect?
initial problem- releases thyroid hormone (bc some is stored)
ultimate effect- hypothyroid in 6 months and must take thyroid hormone for the rest of life
What are the 2 names of the iodine solutions used in hyperthyroidism?
saturated solution of KI
Lugol’s solution
What effect is produced by iodide solutions?
inhibit hormone release by blocking proteolysis of TG
What is the disadvantage of using iodide solutions?
effects are not maintained/ hyperthyroid state returns
What is the MOA of thioamides?
inhibit TPO
blocks iodide oxidation leading to iodine organification
inhibits coupling
effect: no thyroid hormone synthesis
What are the ADRs of thioamides?
GI distress
drug-induced lupus
agranulocytosis
What is the boxed warning of thioamides?
WITH PROPYLTHIOURACIL- severe liver toxicity
How is Propylthiouracil’s action different from methimazole?
also inhibits peripheral deiodination of T4
What is the disadvantage of using thioamides?
slow onset of action
Why are beta-blockers used to treat hyperthyroidism?
REDUCE SYMPTOMS
Beta-blockers used to treat hyperthyroidism must not have what kind of activity?
ISA
If beta-blockers are contraindicated for tx of hyperthyroidism, what alternatives can be used?
clonidine, verapamil
Note 
Flashcard (115)