1. Thyroid and Antithyroid Drugs
Chapter 31
Thyroid and Antithyroid Drugs
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

2. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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 TSH
Tertiary: results when the hypothalamus gland does not secrete thyrotropin-releasing hormone, which stimulates the release of TSH
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

4. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Hypothyroidism
Cretinism
Hyposecretion of thyroid hormone during youth
Low metabolic rate, retarded growth and sexual development, possible mental retardation
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

5. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

6. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

7. Hypothyroidism (cont’d)
Common symptoms
Thickened skin
Hair loss
Constipation
Lethargy
Anorexia
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

8. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Thyroid Preparations
levothyroxine (Synthroid, Levoxyl)
Synthetic thyroid hormone T4
liothyronine (Cytomel)
Synthetic thyroid hormone T3
liotrix (Thyrolar)
Synthetic thyroid hormone T3 and T4 combined
thyroid, desiccated (Armour Thyroid, Westhroid)
Desiccated (dried) animal thyroid gland
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

9. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

10. 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?
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.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

11. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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”
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

12. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

13. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

14. 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
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.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

16. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

18. Treatment of Hyperthyroidism (cont’d)
Antithyroid drugs: thioamide derivatives
methimazole (Tapazole)
propylthiouracil
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

19. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

20. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

21. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

22. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

23. Classroom Response 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 one 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

24. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

25. 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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

26. 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)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

27. Classroom Response 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.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

28. 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)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.