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

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

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

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


Hypothyroidism

Cretinism Hyposecretion of thyroid hormone during youth Low metabolic rate, retarded growth and sexual

development, possible mental retardation


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



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



Common symptoms Thickened skin Hair loss Constipation Lethargy Anorexia


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


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


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.


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”


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


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



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.


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


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


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


Treatment of Hyperthyroidism (cont’d)

Antithyroid drugs: thioamide derivatives methimazole (Tapazole) propylthiouracil


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


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


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



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



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.”



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



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



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)



Which would be the best menu choice for a patient who is taking an antithyroid medication?

A.A seafood platter

B.Sushi

C.Tofu burger

D.Pasta with marinara sauce



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