Thyroid and Antithyroid Flashcards
T4 Half life
5-7 days
T3 half life
1 day
Case: Px presents with weight loss, tremors, hyperdefecation and exopthalmos. Dx?
Grave’s Dse (Hyperthyroidism)
Case: Px presents with weight loss, tremors, hyperdefecation and exopthalmos. tx?
Propylthiouracil
Levothyroxine
Methimazole
Inhibits conversion of T4 to T3
Propylthiouracil
Inhibits iodide concentration (Trapping)
Pertechnetate
Perchlorate
Inhibits Iodination/ Organification
Thioamides, Iodide
Inhibits Coupling
Thioamides, Methimazole
Inhibits Hormone release
Li salts, Iodides
Inhibits deiodination
PTU
Inhibits peripheral action (conversion of T4 -> T3)
Beta blocker Corticosteroids Ipodate PTU Amiodarone
PTU
Methimazole
Carbimazole
Thioamides
Thioamides MOA
Irreversible binding of THYROID PEROXIDASE thus inhibiting it
PTU:Methimazole dosage
3 times a day (shorter duration): once a day
Which crosses the placenta?
a. Methimazole
b. PTU
c. Both
C
PTU crosses less readily
Thioamides ADR
Most common: RASH
Rare and dangerous: AGRANULOCYTOSIS
DOC for thyrotoxicosis
Methimazole
*PTU is hepatotoxic
Most common consequence of maternal hypothyroidism treated with Methimazole
Choanal Atresia- nasal septum malformation
Pwede ring aplasia cutis
Recommended for pregnant patients
PTU in the first trimester, Methimazole after
Why switch? PTU is Hepatotoxic!
Useful in preparation in surgery, THYROID STORM
Iodide
2 Phenomenons which Iodide can induce
Jod-Basedow (Hyper), Wolff-Chaikoff (Hypo)
Acute onset of Iodide effects
2-7 days
When is Lugol’s solution and Potassium iodide given?
AFTER admin of antithyroids
*Not before, can induce hyperthyroidism
Fetal goiter in chronic iodide use
Iodide can readily cross the placenta and can be excreted in the breastmilk
*Normal excretion- urine
Iodide ADR
Metallic taste
rash
Fetal goiter
1st isotope used for treatment of thyrotoxicosis
Radioactive Iodine (Oral)
Maximum effects of RI can be felt within
3-6 months
Advantages of RI
Easy admin
Less costly
Absence of pain
Consequence of maternal use of RI during admin or 6-12 mos after
Destruction of Fetal thyroid gland
RI ADR
Sialitis (mag dictionary ka tang ina mo)
RI admin of 100-200mg
Thyroid Cancer
RI admin of 500 mg
Leukemia
they don’t really lower thyroid levels
Beta Blockers
Beta Blockers
antagonize the target organ effects of thyroid hormone
Beta Blockers effect on Hyperthyroid patients
Lowering heart rate especially for those who have palpitations
Reducing tremors
Propanolol is the same with PTU in?
Inhibiting conversion of T4-T3
Main Indication of Propanolol
Thyroid Storm
Difference of propanolol to other B Blockers
Shorter duration (4-6 hrs), must be given 3 times a day (oral)
Case: 55 y/o female with cold intolerance, weight gain, easy fatigability, edema and diffuse goiter. Dx?
Hypothyroidism
Case: 55 y/o female with cold intolerance, weight gain, easy fatigability, edema and diffuse goiter. Tx?
Levothyroxine
Levothyroxine>Liothyronine
Levo (L-T4) is IV, Fair to Good absorption, longer duration (Half life- 7days) and more likely to bind to protein
Liothyronine is not commercially available
Levothyroxine MOA
Suppression of TSH
Drug that can increase serum levels of T4
Estrogen- increases TBG
*Acute infectious hepatitis
Drugs that decrease TBG
Androgens, Glucocorticoids
*Nephrotic Syndrome
Drugs affecting Thyroid Hormone Binding
Phenytoin
Diazepam
Salicylates
Drugs that interfere absorption of L-T4
Cholestyramine
Al Hydroxide
Fe Sulfate
Ca
Thyroid hormone dose requirements _____ during pregnancy
a. Inc
b. Dec
c. Stay the same
A
