1. Thyroid and Antithyroid Drugs
Chapter 31
Thyroid and Antithyroid Drugs
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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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3. Hypothyroidism: Deficiency in Thyroid Hormones
Primary: abnormality in the thyroid gland itself
Secondary: results when the pituitary gland is dysfunctional and does not secrete thyroid-stimulating hormone (TSH)
Tertiary: results when the hypothalamus gland does not secrete thyrotropin-releasing hormone, which stimulates the release of TSH
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4. Hypothyroidism (Cont.)
Congenital hypothyroidism
Hyposecretion of thyroid hormone during youth
Low metabolic rate, retarded growth and sexual development, possible mental retardation
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5. Hypothyroidism (Cont.)
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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6. Hypothyroidism (Cont.)
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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7. Hypothyroidism (Cont.)
Common symptoms
Thickened skin
Hair loss
Constipation
Lethargy
Anorexia
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8. Thyroid Replacement Drugs
Levothyroxine (Synthroid, Levoxyl)
Synthetic thyroid hormone T4
Liothyronine (Cytomel)
Synthetic thyroid hormone T3
Liotrix (Thyrolar)
Synthetic thyroid hormone T3 and T4 combined
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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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10. Audience Response System 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?
The patient is experiencing hyperthyroidism.
The patient is experiencing hypothyroidism.
The patient’s thyroid hormone levels are within normal limits.
The patient’s thyroid hormone levels are still fluctuating.
Correct answer: C
Rationale: The term euthyroid means that normal thyroid hormone levels have been achieved.
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Indications
Replace what the thyroid gland itself cannot produce to achieve euthyroid condition (Levothyroxine)
Diagnosis of suspected hyperthyroidism (as in a TSH-suppression test)
Prevention or treatment of various types of goiters
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Indications (Cont.)
Replacement hormonal therapy in patients whose thyroid glands have been surgically removed or destroyed by radioactive iodine in the treatment of thyroid cancer or hyperthyroidism
Hypothyroidism of pregnancy
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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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14. Audience Response System 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
inadequate doses of the medication.
possible overdose of the medication.
worsening of the underlying disease.
drug interactions with another medication.
Correct answer: A
Rationale: A return of the symptoms of hypothyroidism indicates that the patient is receiving inadequate doses of the medication.
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15. 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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16. Hyperthyroidism (Cont.)
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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17. 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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18. Treatment of Hyperthyroidism (Cont.)
Antithyroid drugs: thioamide derivatives
Methimazole (Tapazole)
Propylthiouracil
Radioactive iodine (iodine 131)
Potassium iodine
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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, and potential drug interactions.
Obtain baseline vital signs and weight.
Cautious use is advised for those with cardiac disease or hypertension and for pregnant women.
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21. Nursing Implications (Cont.)
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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22. Nursing Implications (Cont.)
Teach patients to take thyroid drugs once daily in the morning to decrease the likelihood of insomnia if taken later in the day.
Teach patients to take the medications at the same time every day and not to switch brands without primary care provider approval.
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23. Audience Response System Question
Which information will the nurse include when teaching a patient about thyroid replacement therapy?
“Take the medication before bed.”
“You will experience beneficial effects of the drug after 1 week of treatment.”
“Stop taking the drug if you experience insomnia.”
“Take the medication on an empty stomach.”
Correct answer: D
Rationale: Thyroid replacement drugs are best taken ½ to 1 hour before breakfast on an empty stomach to enhance their absorption orally, maintain constant hormone levels, and help prevent insomnia. These medications should never be abruptly discontinued, and lifelong therapy is usually the norm. Patients should be advised that it may take up to 3 to 4 weeks to see the full therapeutic effects of thyroid drugs.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

24. Nursing Implications (Cont.)
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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25. Nursing Implications (Cont.)
Teach patients the importance of alerting health care providers of thyroid medication use.
May enhance activity of anticoagulants
Patients with diabetes may need increased dosages of hypoglycemic medications.
May decrease serum digoxin levels
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26. Nursing Implications (Cont.)
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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27. Audience Response System Question
Which would be the best menu choice for a patient who is taking an antithyroid medication?
A seafood platter
Sushi
Tofu burger
Pasta with marinara sauce
Correct answer: D
Rationale: The patient should avoid foods high in iodine, such as soy, tofu, and seafood.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

28. Nursing Implications (Cont.)
Monitor for therapeutic response.
Thyroid drugs: decreased symptoms of hypothyroidism, improved energy levels, improved mental and physical stamina
Antithyroid drugs: no evidence of hyperthyroidism
Monitor for adverse effects.
Thyroid drugs: cardiac dysrhythmia
Antithyroid drugs: leukopenia (manifested as fever, sore throat, lesions)
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