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
pg. 1
,2
○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
· 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,
pg. 2
,3
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
■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
pg. 3
, 4
● 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.
● Minimizing Adverse Effects:
Agranulocytosis(develops during the first 2 months of
therapy): Inform patients about early signs of
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
pg. 1
,2
○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
· 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,
pg. 2
,3
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
■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
pg. 3
, 4
● 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.
● Minimizing Adverse Effects:
Agranulocytosis(develops during the first 2 months of
therapy): Inform patients about early signs of
pg. 4
