Thyroid and Antithyroid Drugs Flashcards
dopamine agonists cause an ↑ / ↓ in GH
↓
iodide ion is taken in to the thyroid gland via ______ (transporter)
Na/I symport
T3/T4 is more potent
T3
thyroid hormones are metabolized by:
- deiodinization (most important)
- ______
- _______
glucorondiation and sulfation
the use of propylthiouracil can inhibit ________ (enzyme) and can low T3 levels
5’ deiodinase enzyme
what drugs can cause low T3 levels by inhibiting 5’ deiodinase?
- propylthioruacil
- propranolol
- corticosteroids
- amiodarone
of the enzymes that metabolize thyroid hormones, which ones are inducible?
- deiodinase
- UDP glucuronosyltransferase
_______ is the most common cause of hypothyroidism in the US and _______ is the most common cause worldwide
Hashimoto’s = US
iodine deficiency = worldwide
lithium can cause _____thyroidism
hypothyroidism
_______ is the hormone preparation of choice for thyroid hormone replacement therapy
synthetic levothyroxine (T4)
cardinal features of myxedema coma include: (3)
how would you treat these patients
- hypothermia
- respiratory depression
- ↓ consciousness
seen in severe and long standing form of HYPOthyroidism
give them T3 and T4 via IV
↑ estrogen will lead to ↓/ ↑ serum levels of thyroid hormones
↓; because estrogen ↑’s the serum concentration of thyroxin binding globulin (TBG)
what are 3 reasons you would give a higher dose of synthetic T4 in pregnant patients?
- estrogen induces and ↑ concentration fo TBG
- expression of 5’ deiodinase by placenta
- small amount passes from mother to uterus
what sit he treatment plan for a patient with congenital hypothyroidism
must administer early and quickly to prevent long term effects; if levothyroxine (synthetic T4) is given within the first 2 weeks of life, normal physical and mental development can be achieved.
thioamides such as _______ and propylthiouracil inhibit the_________ enzyme in the thyroid
- methimazole
Thioperoxidase enzyme (TPO) - inhibit the formation of thyroid hormones
of the thioamides, why is ________ preferred over the other in treatment of severe hyperthyroid and thyroid storm?
propylthiouracil because it also partially inhibits the peripheral dedication of T4 to T3 (methimazole does NOT)
of the thoamides which one is more teratogenic?
methimazole
what are the adverse effects seen with thioamides?
which one is most common and which is the most serious?
- urticarial rash (most common)
- agranulocytosis (most serious)
- hepatotoxicity
- vasculitis
- teratogenicity
methimazole is preferred over PTU except in ________
first trimester of pregnancy and thyroid storm
which of the thioamides is more hepatotoxic?
Propylthiouracil (PTU)
what is the effect of iodides in treating thyroid conditions?
iodides cause the thyroid gland to shut down;
used to treat thyroid storm, preoperative preparation for surgery of the thyroid and radiation emergencies involving release of radioactive iodine
how does hyperthyroidism cause catecholamine excess like manifestations such as HTN, tachycardia, lid lag, sweating, etc even though catecholamine levels are NOT increased
- they ↑ the expression of β adrenergic receptors
_______ (drug family) is used to treat the “catecholamine excess like” manifestations
β blockers
what is your β blocker of choice in a thyroid storm
propanolol; it has peripheral inhibition of deiodinization of T4 to T3 (like PTU)
in a patient whom β blockers are contraindicated, what 2 drugs can be used to control tachycardia?
- diltiazem
- verapamil
(non dihydropyradine calcium channel blocking agents)
β blockers can be contradicted in COPD patients
glucocorticoids MOA and use
inhibits the peripheral conversion of T4 to T3 and promotes vasomotor stability
useful in thyroid storm
how do bile acid sequestrates help treat thyroid storm?
cholestyramine and other bile acid sequestrates bind to and prevent the enterohepatic cycling of thyroid hormones
________ is the preferred treatment for HYPERthyroidism
radioiodine therapy; it destroys the thyroid parenchyma
a patient with hyperthyroidism develops an infection causing an acute exacerbation of hyperthyroidism. what would you give to treat this patient
diagnosis: thyroid storm (4P’s + bile acid sequestrate)
- PTU
- Potassium iodides
- propranolol
- prednisone (corticosteroids)
- bile acid sequestrants
in treating thyrotoxicosis in pregnancy, _______ is given in the first trimester of pregnancy and then _____ is given for the remainder of the pregnancy to avoid _________
1st trimester: PTU
2nd trimester: Methimazole to avoid potential liver damage
a person taking amiodarone shows symptoms of hyperthyroidism. panel shows ↓ TSH and ↑ T4 and T3.
what are the two types of thyrotoxicosis that can be caused by amiodarone and how can you tell the differenced?
- ↑ synthesis of thyroid hormones
- destructive thyroiditis
do a reactive iodine uptake: 1st type where there is ↑ synthesis will show uptake of the iodine but the destructive type will not take it up.
lab values are the same for both types
a person taking amiodarone has ↓ TSH and ↑ T4 and T3. the did NOT take up the radioactive iodine when administered. what do you give to treat his condition
destructive thyroiditis caused by amiodarone
treat with GLUCOCORTICOIDS
_________ (drugs) are given to treat amiodarone induced thyrotoxicosis where there is ↑ synthesis of thyroid hormones
anti-thyroid hormones
pretibial myxedema is a clinical feature of what thyroid pathology
grave’s disease
scalloped colloid on histology of thyroid. what type of HS reaction is this disease
dx: Grave’s
Type 2 HS
anti-thyroglobulin antibodies and anti-thyroid peroxidase (TPO) antibodies are found in a patient. what is a likely complication of this condition
dx. Hashimoto’s
↑ risk for developing other autoimmune conditions: DM1, SLE, myasthenia gravis, pernicious anemia
↑ risk for B cell lymphoma (MALToma)
what is the Wolf Chaikoff effect?
High-dose iodide blocks the release of T4 and T3 into circulation and transiently inhibits thyroid hormone synthesis by blocking the organification step
which drugs most commonly can HYPOthyroidism
- sulfonamides
- lithe
- amiodarone
sulfonylureas can cause ___thyroidism
hypothyroidism
tyrosine kinase inhibitors can cause _____thyroidism
hypothyroidism
