thyroid

Question 1

Levothyroxine (T4)/ Synthroid
class
moa
SE

Answer 1

Thyroid hormone replacement
Replace normal levels of T4 and T3
(T4 converted into T3 in periphery)
Palpitations, tachycardia, heat intolerance, anxiety

Long-term elevation of T4 may accelerate cardiac disease & osteoporosis

Question 2

Levothyroxine (T4)/ Synthroid
class

Charcateristics

Answer 2

PO/IV
Oral absorption: 70%
Slow onset
½ life: 1 week – takes 6-8 weeks to achieve steady state

Start low, go slow
Hold/reduce dose if any complaints of angina
Caution: >65 or Hx of CAD; Addison’s: must replace cortisol before fixing thyroid, otherwise can be fatal

Question 3

Thyroid USP (T4, T3)

Armour

Answer 3

Thyroid hormone replacement
Replaces normal levels of T4 and T3

Similar to Synthroid
Desiccated pork thyroid gland
PO
Generally standardized to iodine content

Start low, go slow
Hold/reduce of angina complaints
Caution: >65 or Hx CAD

Question 4

Liothyroinine (T3)

Cytomel

Answer 4

Thyroid hormone replacement
Replaces T3 levels
Similar to T4
Indication: patients w/ intolerance or no improvement to T4 replacement; myxedema coma; Wilson’s syndrome

PO/IV
Oral absorption: 100%
Rapid onset
½ life: several hours
Caution: higher peaks/troughs of T3 may increase risk of CAD and osteoporosis

Question 5

Eqivalent doses of thyroid USP=t3(cytomel)=t4(synthroid)

Answer 5

60mg=25mcg=100mcg

Question 6

Methimazole/ Tapazole
Class
MOa

Answer 6

Thioamide

Inhibits transformation of inorganic iodine to organic iodine, blocking production of thyroxine

Also inhibits coupling of iodotyrosine to form T3 & T4

Minimal effect of blocking peripheral conversion T4 to T3

Question 7

Methimazole/ Tapazole

SE

Answer 7

Hypothyroidism, rash, edema, arthralgia

Agranulocytosis: don’t give > 6-12 months

Question 8

Methimazole/ Tapazole

Char

Answer 8

Indication: hyperthyroidism d/t Grave’s, toxic nodular, toxic multinodular dz, thyroid storm (when given IV)
May be used to control hyperthyroid state until more definitive therapy is used

PO, IV
Dosing to therapeutic state may take days to weeks
Thyroid storm: IV delivery
Doesn’t affect T4 already in gland

CI: Pregnancy, lactation

Question 9

Propylthiouracil (PTU)
class
MOA

Answer 9

Thioamide

Inhibits transformation of inorganic iodine to organic iodine, blocking production of thyroxine

Also inhibits coupling of iodotyrosine to form T3 & T4

Notable effect of blocking peripheral converstion T4 to T3

Question 10

Propylthiouracil (PTU)

SE

Answer 10

Hypothyroidism, rash, edema, arthralgia

Agranulocytosis: don’t give > 6-12 months

Question 11

Propylthiouracil (PTU)

Char

Answer 11

Indication: hyperthyroidism d/t Grave’s, toxic nodular, toxic multinodular dz, thyroid storm (when given IV)
May be used to control hyperthyroid state until more definitive therapy is used

PO. IV
Dosing to therapeutic state may take days to weeks
Doesn’t affect T4 already in gland

CI: Pregnancy (Category D) but safer than Methimazole, used in pregnancy when benefits > risks

Question 12

Propranolol/Inderal

Answer 12

Non-selective beta blocker

Beta-1 & Beta-2 receptor blockade
F
atigue, sedation, impotency, depression

Indication: Blockade of adrenergic symptoms of hyperthyroidism (tachycardia, anxiety); Emergent tx of thyroid storm

Question 13

odine

SSKI

Answer 13

Elemental iodine

Large doses of iodine inhibit release of thyroxine from thyroid gland
Rash, fever
PO/IV

Beneficial effects < 2-3 weeks

Question 14

Radioactive iodine

131I

Answer 14

Radioactive isotope

Radioactive emission of beta particles destruction of thyroid tissue

Few; infrequent SE

Sore throat, swollen salivary glands, mild nausea
Indication: thyroid gland ablation

PO
Takes weeks for complete destruction of gland

CI: Pregnancy (Category X)

Patients will be hypothyroid & require lifelong replacement of exogenous hormone