Thyroid dz Meds

Question 1

etiologies of primary hypothyroidism? etiology of iatrogenic hypothyroidism?

Answer 1

primary: autoimmune phenomena (Hashimoto’s dz), malnutrition, deficient iodine intake
iatrogenic: surgery or radioactive ablation

Question 2

what does secondary hypothyroidism imply? tertiary?

Answer 2

secondary implies pituitary dysfunction

tertiary implies hypothalamic dysfunction

Question 3

what can inflammation of the thyroid gland result in? thyroiditis course?

Answer 3

in initial excess thyroid release which is then followed by a period of insufficient thyroid hormone release
course of thyroiditis is usu limited and reversible except in Hashimoto’s

Question 4

clinical findings of hypothyroidism?

Answer 4

fatigue, weakness, cold intolerance, constipation, thinning hair, bradycardia, poor concentration
if chronic can result in respiratory depression, hypothermia, coma (myxedema coma), death
infants w/unrecognized and untreated hypothyroidism develop cretinism

Question 5

3 hypothyroid tx options?

Answer 5

levothyroxine (T4)/synthroid
thyroid USP (T4, T3)/Armour thyroid
Liothyronin (T3)/Cytomel

Question 6

class of levothyroxine/synthroid? indications? MOA?

Answer 6

class: thyroid hormone replacement, synthetic T4, dosed in mcg
indications: hypothyroidism, also TSH suppression in select cases of thyroid nodules and thyroid CA
MOA: replaces normal levels of T4 and T3 (T4 converted to T3 in periphery)

Question 7

how to give levothyroxine/synthroid? how long to tx? when to hold or reduce dose?

Answer 7

give PO/IV once a day
oral absorption ~70%
slow onset of action
1/2 life 1 wk
takes 6-8 wks to achieve steady state
tx usu lifelong - need to follow pts clinical response and serum TSH
hold or reduce dose if any complaints of angina
begin at low dose and advance dosage slowly in pts over 65 or in any pts w/hx of coronary artery dz

Question 8

SEs of levothyroxine/synthroid? long term elevation of T4 can cause what?

Answer 8

SEs: toxicity directly related to thyroxine level and manifests as palpitations, tachycardia, intolerance to heat and anxiety
long term elevation of serum T4 may accelerate cardiac dz and osteoporosis

Question 9

in pts w/Addison’s dz and hypothyroidism what needs to be replaced first?

Answer 9

need to give cortisol first! then thyroid otherwise can be fatal

Question 10

60 mg of Thyroid USP produces about an equivalent effect of how much synthroid?

Answer 10

60 mg of Thyroid USP = about 100 mcg of Synthroid (synthetic T4)

Question 11

class of thyroid USP/armour? indications? mOA? how to give? how to dose?

Answer 11

class: thyroid hormone (T4, T3, T2, T1) from desiccated animal thyroid gland
indications: hypothyroidism
MOA: replaces both T4 and T3
give PO, generally standardized to iodine content
initiate medication at low dose and increase dosage according to pt response, more cautious dosing in pts over 65 or if hx of cardiac dz

Question 12

SEs of thyroid USP/Armour? what do you need to follow? hold or reduce if complaints of what? how to dose?

Answer 12

SEs: similar to thyroxine/synthroid
follow pts clinical response and serum TSH
hold or reduce dose if any complaints of angina
begin at low dose and advance dose slowly in pts over 65 or in those w/hx of CAD

Question 13

class of liothyronine/cytomel? indications? can also be used for what? MOA?

Answer 13

class: thyroid hormone replacement (synthetic T3) dosed in mcg
indications: hypothyroidism that has demonstrated intolerance to T4 replacement therapy or no improvement on T4 replacement therapy, myxedema coma
also used for Wilson’s syndrome
MOA: replaces T3

Question 14

how to give liothyronine/cytomel? SEs? higher peaks and troughs of T3 can increase what risk?

Answer 14

give PO/IV, 100% oral absorption, rapid onset of action, half life of several hours
SEs: similar to T4
higher peaks and troughs of T3 may increase risk of coronary artery disease and osteoporosis

Question 15

equivalent dosings between thyroid USP, synthroid and cytomel?

Answer 15

60 mg thyroid USP ~ = 100 mcg of T4 (synthroid) ~ = 25 mcg of T3 (cytomel)

Question 16

most common underlying cause of hyperthyroidism?

Answer 16

autoimmune - Grave’s - antibodies stimulate TSH receptor sites on the thyroid gland
can also be caused by thyroiditis

Question 17

what is thyroiditis facticia?

Answer 17

excess administration of thyroid hormone, either inadvertent or intentional

Question 18

clinical findings of hyperthyroidism include? hyperthyroidism places pt at increased risk for what?

Answer 18

nervousness, tachycardia, wt loss, heat intolerance, sweating, diarrhea, generalized weakness
places the pt at increased risk for osteoporosis and cardiac dz
if dt Grave’s dz often accompanied by presence of goiter and exophthalmos

Question 19

what is pretibial myxedema? associated with what? dt what?

Answer 19

lesions of non-pitting edema that occur in association w/Grave’s dz
appear on anterior or lateral aspects of legs in ~0.5-5% of pts w/Grave’s dz
dt deposition of hyaluronic acid in dermis and subcutis in thyroid dz
proposed mechanism is that fibroblasts are stimulated to produce high amounts of glycosaminoglycan dt exposure to thyroid hormones

Question 20

tx of hyperthyroidism involves what? what can be used to block teh adrenergic ssxs of hyperthyroidism?

Answer 20

tx involves medications that interrupt thyroid hormone synthesis and/or release of thyroid hormone as well as interruption of peripheral conversion of T4 to T3
beta blockers are often used to block adrenergic ssxs of hyperthyroid state

Question 21

definitive tx of hyperthyroidism?

Answer 21

surgical removal of radioactive iodine and ablation of the thyroid gland
after this though pts are rendered hypothyroid and will need exogenous thyroid hormone for the rest of their lives

Question 22

hyperthyroid tx options?

Answer 22

methimazole
propylthiouracil
propanolol
iodine
radioactive iodine

Question 23

class of methimazole/tapazole? indications? place in tx of hyperthyroidism? after tx is discontinued what can happen? tx failure or recurrence suggests what tx is needed?

Answer 23

class: thioamide
indications: hyperthyroidism dt Grave’s dz, toxic nodular or toxic multinodular dz and thyroid storm (when give IV)
can allow for better control of hyperthyroid state until more definitive tx is used
pts may occasionally achieve a euthyroid state after tx is discontinued
tx failure or reucrrent of hyperthyroid state suggests more definitive tx is necessary

Question 24

MOA of methimazole/tapazole? how to give? where does it concentrate? effects on thyroglobulin already stored in thyroid gland?

Answer 24

MOA: inhibits transformation of inorganic iodine to organic iodine, therefore blocking production of thyroxine, also inhibits coupling of iodotyrosine to form T3 and T4, very minimal effect of blocking the peripheral conversion of T4 to T3
give PO, IV (thyroid storm)
concentration occurs in thyroid
does not affect thyroglobulin already stored in thyroid gland

Question 25

SEs of methimazole/tapazole? feared SE? do not give when?

Answer 25

SE: may cause hypothyroidism, rash, edema, arthralgias
agranulocytosis is a feared SE, drug is usu not given beyond 6-12 mo period
do not give during PG or lactation as it crosses the placenta and into mother’s milk

Question 26

class of propylthiouracil (PTU)? indications? allows for what in regards to control? potential effect after discontinuation?

Answer 26

class: thioamide
indications: hyperthyroidism dt Grave’s, toxic nodular or toxic multinodular dz and thyroid storm (when to give IV)
may allow for better control of hyperthyroid state until more definitive tx is used
pts may occasionally achieve euthyroid state after tx is discontinued

Question 27

MOA of propylthiouracil (PTU)? notable effect?

Answer 27

MOA: inhibits transformation of inorganic iodine to organic iodine, blocking the production of thyroxine and inhibits the coupling of iodotyrosine to form T3 and T4
notable effect of blocking peripheral conversion of T4 to T3

Question 28

how to give propylthiouracil (PTU)? commonly used how? effects on T4 and thyroglobulin already stored in thyroid gland?

Answer 28

give PO, IV, may take wks to achieve therapeutic state, thus not used as an oral agent for thyroid storm
commonly used before definitive tx by surgery or radioactive iodine ablation
affects the production of thyroid hormone but does not affect the T4and thyroglobulin already stored in thyroid gland

Question 29

SEs of propylthiouracil? most feared SE? how long can you give? PG category?

Answer 29

SE: hypothyroidism, rash, edema, arthralgias
most feared SE is agranulocytosis
drug usu not given beyond 6-12 mo period
PG category D, but considered safer than methimazole and used in PG when benefit outweighs potential risks

Question 30

class of propanolol/inderal? indications? MOA? how to give? SEs?

Answer 30

class: non-selective beta blocker
indications: blockade of adrenergic sxs of hyperthyroidism, emergent tx of thyroid storm
MOA: beta 1 and beta 2 receptor blockade
give PO/IV
SEs: sedation, fatigue, impotency or depression

Question 31

class of iodine/SSKI? indications? MOA? how to give? SES?

Answer 31

class: elemental iodine
indications: hyperthyroidism, thyroid storm
MOA: large doses of iodine inhibit the release of thyroxine from the thyroid gland
give PO/IV, usu given in form of supersaturated potassium iodide
SEs: rash, fever, beneficial effects usu don’t last longer than 2-3 wks as thyroid appears to adapt

Question 32

definitive tx for hyperthyroidism?

Answer 32

radioactive iodine ablation

can also be used in selected cases of thyroid gland cancer

Question 33

SEs of radioactive iodine? what thyroid state does a pt need to be in before starting radioactive iodine tx?

Answer 33

b/c the thyroid gland absorbs almost all the iodine, there are generally minimal systemic effects
can cause tenderness, swelling during initial tx (can use acetaminophen to relieve), N/V may occur, salivary glands may swell
prior to tx pt needs to be in euthyroid state by anti-thyroid drugs and/or doses of supersaturated potassium iodide

Question 34

radioactive iodine PG category? extremely high doses can result in what? following administration what will most need to be tx’ed with?

Answer 34

PG category X
extremely high doses may result in bone marrow depression (transient usu)
following administration will most likely need to be tx’ed with lifelong thyroid replacement

Question 35

class of radioactive iodine? indications? MOA? how to give? how long before it works?

Answer 35

class: radioactive isotope
indications: thyroid gland ablation in cases of Grave’s dz, thyroid nodules, in some cases of thyroid cancer
MOA: radioactive emission of beta particles results in destruction of thyroid tissue
give orally, generally takes weeks for destruction of thyroid gland tissues to be complete

Question 36

conversation you will need to have with men regarding radioactive iodine tx for hyperthyroidism?

Answer 36

can have decreased sperm counts and temporary infertility for a period of roughly 2 years
may need to discuss sperm banking w/a male partner who is expecting several doses for thyroid CA

Question 37

what actions do you need to limit 1 day after RAI? what actions do you need to limit 2-3 days after RAI? what actions do you need to limit 5-11 days after RAI?

Answer 37

for 1 day after RAI: do not return to work, limit time in public places, do not travel by airplane or public transportation
for 2-3 days after RAI: do not travel on a prolonged car trip with others, maintain prudent distances from others (~3 ft), drink plenty of fluids, do not prepare foods for others, do not share utensils with others, flush the toilet 2-3 times after use
for 5-11 days after RAI: sleep in a separate bed (~7 feet of separation), avoid prolonged close contact w/children and PG women

Question 38

whom can we never give RAI to?

Answer 38

should never be given to PG woman, can irreversibly damage the fetal thyroid tissue or to a nursing mother as it can reach the infant through breast milk
PG should be delayed at least 6-12 mos after RAI tx since tx exposes ovaries to radiation

Question 39

what is a thyroid storm?

Answer 39

most severe potential manifestation of hyperthyroidism
ssxs: high fever, irritability, delirium, vomiting, diarrhea, dehydration, hypotension, vascular collapse
coma and death can occur

Question 40

when can a thyroid storm occur?

Answer 40

can occur in hyperthyroid pts who become septic

pts undergoing surgery for hyperthyroidism

Question 41

how to tx a thyroid storm?

Answer 41

first stabilize pt
then generally includes beta blockade as well as IV PTU or IV methimazole and IV iodine to “stun” the thyroid gland’s ability to utilize iodine to synthesize thyroid hormone
possibly anti-pyretics for fever