Thyroid (Exam 3) Flashcards by Olivia Hofer

thyroid pathway

anterior pituitary –> TSH –> thyroid –> thyroxin –> growth and metabolism

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hypothalamus hormone

TRH - thyroid releasing hormone

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anterior pituitary hormone

TSH - thyroid stimulating hormone

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most abundant part of the thyroid hormone

thyroxine (T4)

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what controls the rate of release of T4 and T3

TSH

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what binds T3 and T4 in the bloodstream

thyroid-binding globulins (TBGs)

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hyperthyroidism

too much thyroid hormone
metabolism speeds up

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hypothyroidism

too little thyroid hormone
metabolism slows down

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primary causes of hypothyroidism

iodine deficiency
hashimoto disease
subacute thyroiditis
iatrogenic (irradiation, surgery)
thyroid nodules
drugs

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primary causes of hyperthyroidism

iodine excess
geaves disease
subacute thyroiditis
thyrotoxicosis factitia
thyroid nodules
drugs

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s/s of hypothyroidism

tiredness
dry, course hair
brittle nails
puffy face + eyes
slow heart rate
weight gain

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s/s of hyperthyroidism

bulging eyes
unblinking stare
downward gaze
rapid heartbeat
weight loss

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normal range of TSH

0.5-4.5 mlU/mL

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normal range of free T4

0.8-1.7 ng/dL

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normal range of free T3

2.3-4.2 ng/dL

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low T3 uptake is associated with

hypothyroid conditions

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high T3 uptake is associated with

hyperthyroid conditions

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which tests are more suggestive of hashimoto’s disease

thyroid peroxidase antibody (TPOAb)
thyroglobulin antibodies (TGAb)

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TSH and free T3/T4 in primary hypothyroidism

TSH increased
free T3/T4 decreased

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which tests are more suggestive of graves disease

TSH receptor antibody (TSHR-Ab)

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TSH and free T3/T4 in sec/tertiary hypothyroidism

TSH decreased
free T3/T4 decreased

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TSH and free T3/T4 in subclinical hypothyroidism

TSH increased
free T3/T4 normal

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TSH and free T3/T4 in primary hyperthyroidism

TSH decreased
free T3/T4 increased

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TSH and free T3/T4 in subclinical hyperthyroidism

TSH decreased
free T3/T4 normal

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most common cause of sec/tertiary hyperthyroidism

TSH-secreting pituitary adenoma

patients with sec/tertiary hyperthyroidism have

high serum TSH despite high free T4 and T3 concentrations

therapy for TSH secreting adenoma

surgical resection of tumor

radioactive iodine uptake (RAIU) measurement are studied

after 4-6 hours and 24 hours

normal RAIU

4-6 hours = 6-18% 24 hours = 10-30%

decreased RAIU

suggests hashimotos

increased RAIU

suggests graves

uneven RAIU

suggests nodule

which type of nodule is typically benign

hot

euthyroid-sick syndrome

transient elevations in serum TSH concentrations during recovery from non-thyroidal illness

when to take thyroid measurements in pts with recent illness

TSH and free T4 repeated 4-6 weeks

treatment of hypothyroidism

levothyroxine (T4) thyroid USP (T4:T3 4:1) liothyronine (T3)

drug of choice for hypothyroidism

levothyroxine

when to take levothyroxine

in morning on empty stomach 30-60 mins before food 4 hours before or after drugs that interfere with absorption

weight based dosing for levothyroxine

1.6 mcg/kg/day

dosing for >60 years without cardiac disease OR <60 years with cardiac disease

25-50 mcg/day

dosing for >60 years with cardiac disease

12.5-25 mcg/day

most reliable guide for evaluating adequacy of thyroid replacement dosage

TSH

goal of therapy with levothyroxine

euthyroid state with TSH in range of 0.5-4.5 mlU/mL

how long does levo take to work?

2-4 weeks after starting therapy

monitor serum TSH and T4 levels _____ after initiating therapy or dose adjustment

6-8 weeks

how often is TSH and T4 checked after normalization

6 months then annually

central hypothyroidism

various disorders affecting either pituitary gland or hypothalamus

are measurements of serum TSH of value in central hypothyroidism

human thyroid gland T4:T3

13.1:16.1

combination therapy may be beneficial in

pts who remain symptomatic in spite of T4 replacement and normal TSH conc.

10 mlU/mL in nonpregnant adults with subclinical hypothyroidism

treat with T4

7-9.9 mlU/mL in nonpregnant adults <65-70 years old with subclinical hypothyroidism

treat with T4

7-9.9 mlU/mL in nonpregnant adults >65-70 years old with asymptomatic subclinical hypothyroidism

observe

7-9.9 mlU/mL in nonpregnant adults >65-70 years old with symptomatic subclinical hypothyroidism

treat with T4

4.6-6.9 mlU/mL n nonpregnant adults <65-70 years old with asymptomatic subclinical hypothyroidism

observe

4.6-6.9 mlU/mL n nonpregnant adults <65-70 years old with symptomatic subclinical hypothyroidism

treat with T4

4.6-6.9 mlU/mL n nonpregnant adults >65-70 years old subclinical hypothyroidism

observe

thyroid requirements ____ during pregnancy and TSH range is ____

increase lower

dose of levothyroxine in pregnancy

increase by 25-30% 2 additional tabs a week

when to check TSH levels in pregnancy

every 4 weeks during first half of pregnancy then every 4-6 weeks after

myxedema coma

life-threatening state of decompensated hypothyroidism

clinical features of myxedema coma

decreased mental status hypothermia bradycardia hyponatremia hypoglycemia hypotension

treatment of myxedema coma

levothyroxine IV followed by daily doses WITH OR WITHOUT triiodthyronine IV

PO to IV ratio of levothyroxine

PO 1 : 0.75 IV

pharmacological therapy in hyperthyroidism

thioureas (thionamides) beta blockers radioactive iodine iodides

thioureas (thionamides)

propythiouracil (PTU) methimazole (MMI)

which thioureas (thionamides) blocks peripheral T4 to T3 conversion

PTU

what happens to graves patients treated with thionamides over time

TSHR-Sab levels and other immune mediators decrease

improvement with thionamides occurs in _____

6-8 weeks

three mechanisms of spontaneous remission

fall/disappearance of TSHR-Abs destruction of functioning thyroid tissue thyrotropin receptor-blocking antibodies appear

how long to treat hyperthyroidism

12-24 months to induce long-term remission

after stopping hyperthyroid meds, when to monitor?

6-12 months after remission

thionamides adverse effects

agranulocytosis hepatotoxicity (PTU) in first 3 months

which thionamide is preferred

methimazole

if relapse occurs while on thionamides

radioactive iodine is preferred to a second course of antithyroid drugs

beta blockers use in hyperthyroidism

antagonize palpitations, anxiety, tremor, and sweating maintain pulse rate <90 bpm

which beta blockers are used in hyperthyroidism

propranolol nadolol atenolol if COPD/asthma metoprolol if COPD/asthma

radioactive iodine single dose results in

euthyroid state in 40-70% of patients at 6 months

when to give second dose RAI

6 months after first treatment

severe symptoms before RAI therapy

pretreated with thionamides and beta blockers

withhold thionamide ____ prior to RAI administration

4-6 days

iodides are used as

adjunctive therapy as pre-op for surgery inhibit thyroid storm to quickly achieve euthyroidism in thyrotoxic further inhibit thyroid after RAI therapy

iodides are dosed in

drops

surgery pre-treatment

thionamide for 6-8 weeks until euthyroid followed by additon of iodide for 7-10 days propranolol given several weeks before and 7-10 days after

types of iodide

lugols iodine supersaturated potassium iodide

first line hyperthyroidism

radioactive iodine

second line hyperthyroidism

antithyroid drugs

third line hyperthyroidism

surgery

which drug can worsen graves ophthalmopathy

radioactive iodine

risk factors for complications of subclinical hyperthyroidism

>65 years old CVD osteoporosis

no risk factors and TSH 0.1 mU/L to lower limit

observe

no risk factors and TSH <0.1 mU/L with no nodule or symptoms

observe

no risk factors and TSH <0.1 mU/L with symptoms or nodule

treatment

CVD/osteoporosis risk factor with TSH 0.1 mU/L to lower limit

treatment

>65 years risk factor with TSH 0.1 mU/L to lower limit and no symptoms/nodule

observe

>65 years risk factor with TSH 0.1 mU/L to lower limit with symptoms/nodule

treatment

risk factors with TSH <0.1 mU/L

treatment

which pregnant women require therapy for hyperthyroidism

symptomatic and/or moderate to severe overt hyperthyroidism

preferred hyper treatment in pregnant women

PTU before pregnancy and during 1st trimester then MMI for last 2 trimesters with beta blocker

length of beta blocker treatment in pregnant women

2-6 weeks

can pregnant women use RAI therapy

NEVER

thyroid function tests taken ____ throughout pregnancy

every 4-6 weeks

pregnant women with subclinical, asymptomatic and/or mild overt hyperthyroidism

followed with no treatment

thyroid storm

life threatening decompensated hyperthyroidism

thyroid storm levels

free T3 and T4 elevated TSH low

manifestations of thyroid storm

decompensation of organ failure dehydration fever psychosis tachycardia/pnea coma

treatment of thyroid storm

PTU plus inorganic iodide therapy 1 hour after thionamide plus beta blocker plus systemic steroid plus aggressive cooling, ventilator

additional thyroid storm treatment

bile acid sequestrants plasmapharesis avoid aspirin

steroids used in thyroid storm

dexamethasone prednisone methylprednisone hydrocortisone

drugs that decrease T4 and T3 absorption

colestipol, cholestyramine ferrous sulfate sucralfate aluminum hydroxide calcium carbonate

Thyroid (Exam 3) Flashcards

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