Download Pharmacology and the Nursing Process, 4th ed. Lilley/Harrington

Chapter 31
Thyroid and Antithyroid Drugs
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Thyroid Gland

Secretes three hormones essential for proper
regulation of metabolism

Thyroxine (T4)
 Triiodothyronine (T3)
 Calcitonin

Located near the parathyroid gland, which is
responsible for maintaining adequate levels
of calcium in the extracellular fluid
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Hypothyroidism:
Deficiency in Thyroid Hormones



Primary: abnormality in the thyroid gland itself
Secondary: results when the pituitary gland is
dysfunctional and does not secrete TSH
Tertiary: results when the hypothalamus
gland does not secrete thyrotropin-releasing
hormone, which stimulates the release of
TSH
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Hypothyroidism

Cretinism


Hyposecretion of thyroid hormone during youth
Low metabolic rate, retarded growth and sexual
development, possible mental retardation
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Hypothyroidism (cont’d)

Myxedema


Hyposecretion of thyroid hormone during
adulthood
Decreased metabolic rate, loss of mental and
physical stamina, weight gain, loss of hair, firm
edema, yellow dullness of the skin
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Hypothyroidism (cont’d)

Goiter

Enlargement of the thyroid gland
 Results from overstimulation by elevated levels of
TSH
 TSH is elevated because there is little or no
thyroid hormone in circulation
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Hypothyroidism (cont’d)

Common symptoms

Thickened skin
 Hair loss
 Constipation
 Lethargy
 Anorexia
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Thyroid Preparations

levothyroxine (Synthroid, Levoxyl)


liothyronine (Cytomel)


Synthetic thyroid hormone T3
liotrix (Thyrolar)


Synthetic thyroid hormone T4
Synthetic thyroid hormone T3 and T4 combined
thyroid, desiccated (Armour Thyroid,
Westhroid)

Desiccated (dried) animal thyroid gland
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Mechanism of Action


Thyroid preparations are given to replace
what the thyroid gland cannot produce to
achieve normal thyroid levels (euthyroid)
Thyroid drugs work the same way as
endogenous thyroid hormones
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Classroom Response Question
A patient has been taking levothyroxine for 6 months.
After this month’s laboratory work, the nurse
practitioner tells the nurse that the patient is
“euthyroid.” What does that term mean?
A. The patient is experiencing hyperthyroidism.
B. The patient is experiencing hypothyroidism.
C. The patient’s thyroid hormone levels are within
normal limits.
D. The patient’s thyroid hormone levels are still
fluctuating.
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Indications



To treat all three forms of hypothyroidism
Levothyroxine is the preferred drug because its
hormonal content is standardized; therefore, its
effect is predictable
“Euthyroid”
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Indications (cont’d)

Also used for thyroid replacement in patients
whose thyroid glands have been surgically
removed or destroyed by radioactive iodine in
the treatment of thyroid cancer or
hyperthyroidism
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Adverse Effects


Cardiac dysrhythmia is the most significant
adverse effect
May also cause:

Tachycardia, palpitations, angina, hypertension,
insomnia, tremors, headache, anxiety, nausea,
diarrhea, menstrual irregularities, weight loss,
sweating, heat intolerance, fever, others
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Classroom Response Question
A patient who is taking a thyroid replacement
medication tells the nurse that she is starting to
experience cold intolerance, depression, constipation,
and dry skin. The nurse anticipates that these
manifestations are caused by
A. inadequate doses of the medication.
B. possible overdose of the medication.
C. worsening of the underlying disease.
D. drug interactions with another medication.
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Hyperthyroidism:
Excessive Thyroid Hormones

Caused by several diseases
Graves’ disease
 Multinodular disease
 Plummer’s disease (rare)
• Also called toxic nodular disease
 Thyroid storm (induced by stress or infection)
• Severe and potentially life-threatening

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Hyperthyroidism

Affects multiple body systems, resulting in an
overall increase in metabolism






Diarrhea
Flushing
Increased appetite
Muscle weakness
Sleep disorders
Altered menstrual flow





Fatigue
Palpitations
Nervousness
Heat
intolerance
Irritability
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Treatment of Hyperthyroidism


Radioactive iodine (I131) works by destroying
the thyroid gland
Surgery to remove all or part of the thyroid
gland

Lifelong thyroid hormone replacement will be
needed
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Treatment of Hyperthyroidism
(cont’d)

Antithyroid drugs: thioamide derivatives


methimazole (Tapazole)
propylthiouracil
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Antithyroid Drugs


Used to treat hyperthyroidism and to prevent
the surge in thyroid hormones that occurs
after surgical treatment or during radioactive
iodine treatment for hyperthyroidism
May cause liver and bone marrow toxicity
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Nursing Implications



Assess for drug allergies, contraindications,
potential drug interactions
Obtain baseline vital signs, weight
Cautious use advised for those with cardiac
disease, hypertension, and pregnant women
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Nursing Implications (cont’d)


During pregnancy, treatment for
hypothyroidism should continue
Fetal growth may be retarded if maternal
hypothyroidism is untreated during pregnancy

Adjust dosage every 4 weeks to keep TSH at the
lower end of the normal range
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Nursing Implications (cont’d)


Teach patient to take thyroid drugs once daily
in the morning to decrease the likelihood of
insomnia if taken later in the day
Teach patient to take the medications at the
same time every day and not to switch brands
without primary care provider approval
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Classroom Response Question
Which information will the nurse include when teaching
a patient about thyroid replacement therapy?
A. “Take the medication before bed.”
B. “You will experience beneficial effects of the drug
after one week of treatment.”
C. “Stop taking the drug if you experience insomnia.”
D. “Take the medication on an empty stomach.”
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Nursing Implications (cont’d)



Teach patients to report any unusual
symptoms, chest pain, or heart palpitations
Teach patients not to take over-the-counter
medications without primary care provider
approval
Teach patients that therapeutic effects may
take several weeks to occur
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Nursing Implications (cont’d)

Teach patients the importance of alerting
health care providers of thyroid medication
use

May enhance activity of anticoagulants
 Diabetic patients may need increased dosages of
hypoglycemic meds
 May decrease serum digoxin levels
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Nursing Implications (cont’d)

Antithyroid medications

Better tolerated when given with food
 Give at the same time each day to maintain
consistent blood levels
 Never stop these medications abruptly
 Avoid eating foods high in iodine (seafood, soy
sauce, tofu, and iodized salt)
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Classroom Response Question
Which would be the best menu choice for a patient
who is taking an antithyroid medication?
A.
B.
C.
D.
A seafood platter
Sushi
Tofu burger
Pasta with marinara sauce
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Nursing Implications (cont’d)

Monitor for therapeutic response

Thyroid drugs: decreased symptoms of
hypothyroidism, improved energy levels, improved
mental and physical stamina
 Antithyroid drugs: no evidence of hyperthyroid

Monitor for adverse effects


Thyroid drugs: cardiac dysrhythmia
Antithyroid drugs: leukopenia (manifested as
fever, sore throat, lesions)
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