pc5 2.1 thyroid

TRH

hypothalamus releases what in the hypothalamic pituitary thyroid axis

TSH

TRH stimulates the release of what in the anterior pituitary release hormone

thyroglobulin

TSH stimulates follicular cells for what

Na/I symporter

what brings iodine into the cell

pendrin transporter

what moves iodine into the colloid

thyroid peroxidase

what adds iodine to tyrosine to make T3, T4

MIT

Iodine + tyrosine =

DIT

Iodine + MIT =

T3

MIT + DIT =

T4

DIT + DIT =

T3

is T3 or T4 more active

deiodination

___ takes T4 to T3

inactive hormone reverse T3

deiodination leads to T3 or __

T3

is triiodothyronine T3 or T4

T4

is thyroxine T3 or T4

extrathyroidal peripheral tissues

where are deiodinase enzymes found the breakdown T4

no

is thyroid routinely screened for

T1Dm, autoimmune disease, thyroid disease, goiter, hyperthyroidism, neck radiation to thyroid/thyroid surgery, TSH for anyone over 60, on meds with iodine moiety or low idoine intake

ATA/AACE recommend thyroid screening in what patients

older women

AAFP recommend thyroid screening in what patients

women older than 50

ACP recommend thyroid screening in what patients

TSH

what is the most sensitive index for dx for thyroid labs

FT4

what is used with TSH to assess the degree of hypothyroidism

central hypothyroidism

low TSH and low FT4/FT3 indicate what

primary pituitary failure

central hypothyroidism stems from what

primary hypothyroidism

high TSH and low FT4/FT3 indicate what

primary thyroid failure

(pituitary working)

primary hypothyroidism stems from what

primary hyperthyroidism

low TSH and high FT4/FT3 indicate what

secondary hyperthyroidism

(like TSH producing tumor)

high TSH and high FT4/FT3 indicate what

thionamides, iodides, b blockers, RAI, surgery

txs for hyperthyroidism

levothyrosine, thyroid USP, liothyronine, liotrix

txs for hypothyroidism

hashimoto's, surgery, radiation, RAI, post partum thyroiditis, post inflammatory thyroiditis, iodine deficiency, drugs

primary causes of hypothyroidism

amiodarone, lithium

what drugs can cause hypothyroidism

hypothalamic disorders, pituitary disease

secondary causes of hypothyroidism

levothyroxine, liothyronine, liotrix

synthetic tx options for hypothyroidism

thyroid USP

natural tx options for hypothyroidism

T4

does levothyroxine contain T3, T4, or T3 + T4

T3

does liothyronine contain T3, T4, or T3 + T4

T4 + T3

does liotrix contain T3, T4, or T3 + T4

T4 + T3

does thyroid USP contain T3, T4, or T3 + T4

levothyroxine

DOC for hypothyroidism

stable, inexpensive, free of antigenicity

why is levothyroxine DOC for hypothyroidism

T4

___ admin provides pool of thyroid hormone that can convert to active T3

3-5 days

oral levothyroxine takes how long for onset

6-8 hours

IV levothyroxine takes how long for onset

yes

is the brand important to stick to within levothyroxine options

re evaluate and re titrate after at least 6 weeks

AACE recommends what if there is a levothryoxine brand change

TSH should be measured after 8-12 weeks

American thyroid association recommends what if there is a levothryoxine brand change

1.6-1.7 micrograms/kg/day

average dose for levothyroxine

actual body weight

what weight is used for levothyroxine dosing

TSh markedly elevated and otherwise healthy

when should a full replacement dose be started with levothyroxine therapy

milder hypothyroidism, subclinical hypothyroidism

when should a lower replacement dose be started with levothyroxine therapy

25-50 mcg/day

lower levothryoxine dose is what

less than 10

what milder hypothroidism indicated by what TSH

older adults, heart disease

what patients should be started on a levothyroxine dose of 12.5 yo 35 microgram/day

12.5-25 microgram/month or every 6-8 weeks

what interval are dose increases done for in levothyroxine tx

no takes up to 8 weeks

does TSH reflect thyroid in a timely manner

no

should TSH be suppressed below normal range

tachycardia, atrial arrhythmias, impaired ventricular relaxation, reduced exercise performance, and increased risk of cardiac mortality

suppressing TSH with excess levothyroxine therapy could lead to what

2-3 weeks

when do symptoms improve in levothyroxine tx

6 weeks

when do max effects take effect in hypothyroidism tx

TSH, FT4, symptoms

what should be normalized when monitoring levothyroxine at 6-12 weeks

annually

once resolved hypothyroidism, how often is monitoring done

60-70 yo

(because decreased albumin)

dose of levothyroxine should be decreased when patient reaches what age

take 30 to 60 minutes before first meal, or 4 hours after last meal

administration counseling points for levothryoxine

bisphosphonates, rybelsus, wegovy oral

what drugs conflict with the time one should take levothyroxine

take bisphosphonates, wait 30 minutes, take levothyroxine, wait 30-60 minutes, eat breakfast, take other meds

if need to take bisphosphonates with levothyroxine when should each be take

allergic rxn to natural/animal dervied products, excessive bone loss, hf, angina pectoris, MI, Afib

AEs of levothyroxine

lithiu, iodine containing meds-amiodarone

what drugs reduce production of thyroid hormone

food, PPI, BAS, calcium, iron, FeSo4, aluminum, sucralfate so separate meds by 4 hours and food by 30-60min

what drugs decrease absorption of levothyroxine

barbituates, carbamazepine, phenytoin, rifampin, sertraline

(might need higher doses)

what drugs increase metabolism of levothyroxine

estrogen

what increases circulating TBG which binds thyroid

BB, amiodarone, selenium deficiency

what decreases the peripheral conversion of thyroid

H. pylori tx, atrophic gastritits, celiac

what conditions may require higher doses of levothyroxine needed

synthetic

is liothyronine nautral or synthetic

difficult to monitor, higher cost, greater risk of cardiotoxicity, no evidence supporting use over T4

disadvantages of liothyronine

potency varies by product bc based on iodine, potential allergic reaction to pig, instability, difficult monitoring

why is thyroid USP/natural not recommended

iodine content, risk of tyrotoxicosis

why are OTC thyroid products NOT recommended

thyroid takes two hours to absorb

what should be considered when drawing thyroid level

diabetes

what populations are more likely to have hypothyroidism

infertility, obesity, depression, cardiac disease

what special populations can hypothyroid contribute to

stillbirths, lower psychological scores in infants

hypothyroidism can cause what in pregnancy

1st 2 months of gestation, increase dose as soon as pregnancy confirmed

when does thyroid need to be delivered to fetus

40-50%

doses of levothyroxine increase by how much in pregancy

albumin increased, less free hormone

why is more thyroid required in pregnancy

over 65

lower thyroid supplements should be used at what age

higher

(use higher goals)

are TSH levels higher or lower in elderly

4-6

what TSH level is used in person greater than 70-80

conversion of T4 to T3

what does amiodarone impair

levothyroxine-supplement T4

how to treat amiodarone drug induced thyroid disease

thyroid hormone secretion

what does lithium impair

baseline, every 6 months

when should TFTs be monitored in drug induced thyroid disease

few/none symptoms, normal T3/T4, elevated TSH

how does subclinical hypothyroidism present

maybe, consider risk/benefit

should subclinical hypothyroidism be treated

elderly, bone loss, CV risk

when should subclinical hypothroidism not be treated

TSH over 10 or TSH 5-10 with a goiter or positive anti thyroid peroxidase antibodies, prior RAI, symptomatic

when should subclinical be treated

myxedema coma

medical emergency that is a result of severe untreated long standing hypothyroidism

decreased mental status, hypothermia, slowing of multiple organs

myxedema coma leads to what

levothyroxine, liothyronine

tx for myxedema coma for thyroid replecamenet

hydrocortisone, 0.9% NS +/- D5W, 3% NaCL + furosemide, warming blankets, vasopressors

tx for myxedema coma for supplemental therapy

hyperthyroidism

exposure of tissues to excessive T4, T3, or both