1
NR565 Final Exam Study Guide Week
5 Ch. 48,49
● Thyroid Diagnosis & Evaluation
○ What labs are used to diagnose?
■ Tests may include thyroid stimulating hormone (TSH), T4, T3, and thyroid
antibody tests
■ Serum TSH - Used primarily for screening & diagnosis of hypothyroid and
for monitoring replacement therapy. Normal range -0.3-6
● Most sensitive method for diagnosing hypothyroid because the anterior
pituitary is sensitive to changes in thyroid hormone levels
● Can distinguish between primary & secondary hypothyroidism
○ Primary: TSH high
○ Secondary: TSH low, normal or slightly elevated
■ Serum Thyroxine Test - Can measure total T4 or Free T4.
● Normal range - 0.9–2
■ Serum Triiodothyronine Test - Can measure total T3 or Free T3
● Normal range - 80–220
(From the lessons in Week 5 module)
TSH low, T4 high, T3 normal - etiology can be related to exogenous T4 ingestion a concurrent
non-thyroidal illness or amiodarone-induced thyroid dysfunction
Serum TSH is normal or elevated and free T4 and T3 are elevated - possibility of TSH
producing pituitary tumor which would need further eval with MRI
TSH is low, free T4 normal, serum T3 high - primary hyperthyroidism, however other reasons
for this thyroid function test abnormality could be exogenous T3 ingestion or a functioning
adenoma
○ Timeframe for re-check of labs after starting levothyroxine
■ Evaluation should not be done until 6-8 weeks after starting treatment until
the patient achieves a euthyroid state, and then afterwards it can be
checked once a year
■ Target goal is 0.5 to 2 milli-international units/L
○ Signs and symptoms of hypo and hyperthyroidism
pg. 1
, 2
· mild hypothyroidism, symptoms are subtle and may go
unrecognized for what they are
· moderate to severe disease, characteristic signs and
symptoms emerge o face is pale, puffy, and
expressionless o skin is cold and dry o hair is brittle, and
hair loss occurs.
o Heart rate and temperature are lowered o
lethargy, fatigue, and intolerance to cold. Mentation
may be impaired.
o Thyroid enlargement may occur if reduced levels
of T3 and T4 promote excessive release of TSH.
● Weight gain
· Hyperthyroid s/s:
o Heartbeat is rapid and strong, and dysrhythmias
and angina may develop
o nervousness, insomnia, rapid thought flow, and
rapid speech.
o Skeletal muscles may weaken and atrophy o
heat production, increased body temperature,
intolerance to heat o skin that
is warm and moist. o Appetite
is increased.
o weight loss o exophthalmos
● Thyroid Treatment
○ Treatment of thyroid storm
■ PTU
■ High doses of potassium iodine or strong iodine solution are given to
suppress thyroid release
■ Methimazole is given to suppress thyroid hormone synthesis
■ Beta Blockers can be given to reduce HR
■ Sedation, cooling, glucocorticoids & IV fluids can also be given
○ Result of not treating hypothyroidism during pregnancy
pg. 2
,3
■ Can decrease the fetus’s IQ in the first trimester
■ After 2nd trimester, the fetal thyroid gland can supply its own hormones
■ Routine screening for hypothyroid in pregnant women is recommended
■ When pregnant women take thyroid supplements, the dosage is usually
increased by 50% between weeks 4 & 8 of gestation
■ Increase T4 levels by 30% as soon as pregnancy is confirmed
■ Iodine 131 is contraindicated for children. Do not give
○ Medication to treat symptoms of hyperthyroidism (notice this is treating
symptoms and not the hyperthyroidism itself)
■ Methimazole (Tapazole) (First-line drug for Hyperthyroidism)
● Safer & more convenient than PTU, except when breastfeeding
or pregnant
● Avoid in first trimester of pregnancy
● Want to check TSH, T3/T4, LFTs & CBCs
● AE: Agranulocytosis - If the patient develops a fever & sore
throat then report to provider immediately
● Drug Class: Thionamide
● MOA: Therapeutic effects result from blocking synthesis of
thyroid hormones.
§ First, methimazole prevents the oxidation of iodide,
thereby inhibiting incorporation of iodine into tyrosine. §
Second, methimazole prevents iodinated tyrosines from
coupling.
§ Both effects result from inhibiting peroxidase, the
enzyme that catalyzes both reactions.
● Therapeutic Goal: Methimazole has four indications: (1)
reduction of thyroid hormone production in Graves’ disease, (2)
control of hyperthyroidism until the effects of radiation on the
thyroid become manifest, (3) suppression of thyroid hormone
production before subtotal thyroidectomy, and (4) treatment of
thyrotoxic crisis.
● Baseline Data: Obtain serum levels of thyroid-stimulating ●
3hormone (TSH), free triiodothyronine (T3), and free
thyroxine (T4). Check baseline CBC and LFTs prior to initiation.
● Monitoring: Check CBC with differential if signs or symptoms of
infection. Check LFTs if signs or symptoms of liver dysfunction.
● Identifying High-Risk Patients: Methimazole should be
avoided in the first trimester of pregnancy - cause neonatal
hypothyroidism, goiter, and even congenital hypothyroidism
● Evaluating Therapeutic Effects: Monitor for weight gain,
decreased heart rate, and other indications that levels of thyroid
hormone have declined. Laboratory tests should indicate a
decrease in serum free T3 and free T4.
pg. 3
, 4
● Minimizing Adverse Effects: Agranulocytosis(develops during
the first 2 months of therapy): Inform patients about early signs
of agranulocytosis, including fever or sore throat. If follow-up
blood tests reveal leukopenia, methimazole should be stopped.
Hypothyroidism: Methimazole may cause excessive reductions
in thyroid hormone synthesis. If signs of hypothyroidism develop
or if plasma levels of T3 and T4 become subnormal, dosage
should be reduced
**Treatment with methimazole lasts for 1-2 years
● Initial dose: 30–40 mg
● Maintenance dose: 5–15 mg
■ Radioactive Iodine
● Can be used to destroy thyroid tissue in hyperthroid patients
● Effects become apparent within a few days but full effects
develop in 2-3 months
● Low cost, less risks than thyroid surgery & no other tissue in the
body will be injured
● AEs: Brassy taste, burning sensation in mouth, sore gums &
teeth, corrosive injury to GI tract
● Contraindicated in pregnancy, breastfeeding and young children
■ Levothyroxine
● Synthetic preparation of Thyroxine, a natural hormone
● Takes around 1 month of dosing to reach full effects
● AEs: Thyroid Storm - Symptoms of thyrotoxicosis include
tachycardia, angina, tremor, nervousness, insomnia, sweating,
and heat intolerance.
● Use with caution in pts with cardiovascular disease
● Therapeutic effects: Reversal of signs of thyroid deficiency and
an absence of signs of thyroid excess , normalization of
intellectual function, growth, and development should occur. In
children, monthly height measurements demonstrate thyroid
sufficiency, laboratory tests indicate normal plasma levels of TSH
and T4 .
● IV levothyroxine is used for myxedema coma
● Not all levothyroxine preparations have the same drug
bioavailability
● Older adults started on levothyroxine should be started on a low
dose (12.5-25mcg/day) with a gradual increase to avoid cardiac
side effects such as palpitations, angina, or myocardial infarction
that may arise from overstimulation. “Start low and go slow” with
dosing in older adults.
○ Drug/Food/Supplement interactions with levothyroxine
pg. 4
NR565 Final Exam Study Guide Week
5 Ch. 48,49
● Thyroid Diagnosis & Evaluation
○ What labs are used to diagnose?
■ Tests may include thyroid stimulating hormone (TSH), T4, T3, and thyroid
antibody tests
■ Serum TSH - Used primarily for screening & diagnosis of hypothyroid and
for monitoring replacement therapy. Normal range -0.3-6
● Most sensitive method for diagnosing hypothyroid because the anterior
pituitary is sensitive to changes in thyroid hormone levels
● Can distinguish between primary & secondary hypothyroidism
○ Primary: TSH high
○ Secondary: TSH low, normal or slightly elevated
■ Serum Thyroxine Test - Can measure total T4 or Free T4.
● Normal range - 0.9–2
■ Serum Triiodothyronine Test - Can measure total T3 or Free T3
● Normal range - 80–220
(From the lessons in Week 5 module)
TSH low, T4 high, T3 normal - etiology can be related to exogenous T4 ingestion a concurrent
non-thyroidal illness or amiodarone-induced thyroid dysfunction
Serum TSH is normal or elevated and free T4 and T3 are elevated - possibility of TSH
producing pituitary tumor which would need further eval with MRI
TSH is low, free T4 normal, serum T3 high - primary hyperthyroidism, however other reasons
for this thyroid function test abnormality could be exogenous T3 ingestion or a functioning
adenoma
○ Timeframe for re-check of labs after starting levothyroxine
■ Evaluation should not be done until 6-8 weeks after starting treatment until
the patient achieves a euthyroid state, and then afterwards it can be
checked once a year
■ Target goal is 0.5 to 2 milli-international units/L
○ Signs and symptoms of hypo and hyperthyroidism
pg. 1
, 2
· mild hypothyroidism, symptoms are subtle and may go
unrecognized for what they are
· moderate to severe disease, characteristic signs and
symptoms emerge o face is pale, puffy, and
expressionless o skin is cold and dry o hair is brittle, and
hair loss occurs.
o Heart rate and temperature are lowered o
lethargy, fatigue, and intolerance to cold. Mentation
may be impaired.
o Thyroid enlargement may occur if reduced levels
of T3 and T4 promote excessive release of TSH.
● Weight gain
· Hyperthyroid s/s:
o Heartbeat is rapid and strong, and dysrhythmias
and angina may develop
o nervousness, insomnia, rapid thought flow, and
rapid speech.
o Skeletal muscles may weaken and atrophy o
heat production, increased body temperature,
intolerance to heat o skin that
is warm and moist. o Appetite
is increased.
o weight loss o exophthalmos
● Thyroid Treatment
○ Treatment of thyroid storm
■ PTU
■ High doses of potassium iodine or strong iodine solution are given to
suppress thyroid release
■ Methimazole is given to suppress thyroid hormone synthesis
■ Beta Blockers can be given to reduce HR
■ Sedation, cooling, glucocorticoids & IV fluids can also be given
○ Result of not treating hypothyroidism during pregnancy
pg. 2
,3
■ Can decrease the fetus’s IQ in the first trimester
■ After 2nd trimester, the fetal thyroid gland can supply its own hormones
■ Routine screening for hypothyroid in pregnant women is recommended
■ When pregnant women take thyroid supplements, the dosage is usually
increased by 50% between weeks 4 & 8 of gestation
■ Increase T4 levels by 30% as soon as pregnancy is confirmed
■ Iodine 131 is contraindicated for children. Do not give
○ Medication to treat symptoms of hyperthyroidism (notice this is treating
symptoms and not the hyperthyroidism itself)
■ Methimazole (Tapazole) (First-line drug for Hyperthyroidism)
● Safer & more convenient than PTU, except when breastfeeding
or pregnant
● Avoid in first trimester of pregnancy
● Want to check TSH, T3/T4, LFTs & CBCs
● AE: Agranulocytosis - If the patient develops a fever & sore
throat then report to provider immediately
● Drug Class: Thionamide
● MOA: Therapeutic effects result from blocking synthesis of
thyroid hormones.
§ First, methimazole prevents the oxidation of iodide,
thereby inhibiting incorporation of iodine into tyrosine. §
Second, methimazole prevents iodinated tyrosines from
coupling.
§ Both effects result from inhibiting peroxidase, the
enzyme that catalyzes both reactions.
● Therapeutic Goal: Methimazole has four indications: (1)
reduction of thyroid hormone production in Graves’ disease, (2)
control of hyperthyroidism until the effects of radiation on the
thyroid become manifest, (3) suppression of thyroid hormone
production before subtotal thyroidectomy, and (4) treatment of
thyrotoxic crisis.
● Baseline Data: Obtain serum levels of thyroid-stimulating ●
3hormone (TSH), free triiodothyronine (T3), and free
thyroxine (T4). Check baseline CBC and LFTs prior to initiation.
● Monitoring: Check CBC with differential if signs or symptoms of
infection. Check LFTs if signs or symptoms of liver dysfunction.
● Identifying High-Risk Patients: Methimazole should be
avoided in the first trimester of pregnancy - cause neonatal
hypothyroidism, goiter, and even congenital hypothyroidism
● Evaluating Therapeutic Effects: Monitor for weight gain,
decreased heart rate, and other indications that levels of thyroid
hormone have declined. Laboratory tests should indicate a
decrease in serum free T3 and free T4.
pg. 3
, 4
● Minimizing Adverse Effects: Agranulocytosis(develops during
the first 2 months of therapy): Inform patients about early signs
of agranulocytosis, including fever or sore throat. If follow-up
blood tests reveal leukopenia, methimazole should be stopped.
Hypothyroidism: Methimazole may cause excessive reductions
in thyroid hormone synthesis. If signs of hypothyroidism develop
or if plasma levels of T3 and T4 become subnormal, dosage
should be reduced
**Treatment with methimazole lasts for 1-2 years
● Initial dose: 30–40 mg
● Maintenance dose: 5–15 mg
■ Radioactive Iodine
● Can be used to destroy thyroid tissue in hyperthroid patients
● Effects become apparent within a few days but full effects
develop in 2-3 months
● Low cost, less risks than thyroid surgery & no other tissue in the
body will be injured
● AEs: Brassy taste, burning sensation in mouth, sore gums &
teeth, corrosive injury to GI tract
● Contraindicated in pregnancy, breastfeeding and young children
■ Levothyroxine
● Synthetic preparation of Thyroxine, a natural hormone
● Takes around 1 month of dosing to reach full effects
● AEs: Thyroid Storm - Symptoms of thyrotoxicosis include
tachycardia, angina, tremor, nervousness, insomnia, sweating,
and heat intolerance.
● Use with caution in pts with cardiovascular disease
● Therapeutic effects: Reversal of signs of thyroid deficiency and
an absence of signs of thyroid excess , normalization of
intellectual function, growth, and development should occur. In
children, monthly height measurements demonstrate thyroid
sufficiency, laboratory tests indicate normal plasma levels of TSH
and T4 .
● IV levothyroxine is used for myxedema coma
● Not all levothyroxine preparations have the same drug
bioavailability
● Older adults started on levothyroxine should be started on a low
dose (12.5-25mcg/day) with a gradual increase to avoid cardiac
side effects such as palpitations, angina, or myocardial infarction
that may arise from overstimulation. “Start low and go slow” with
dosing in older adults.
○ Drug/Food/Supplement interactions with levothyroxine
pg. 4
