Thyroid and Antithyroid Drugs Chapter 31 Thyroid and Antithyroid Drugs Copyright © 2017, Elsevier Inc. All rights reserved.

Copyright © 2017, Elsevier Inc. All rights reserved. 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 © 2017, Elsevier Inc. All rights reserved.

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 Copyright © 2017, Elsevier Inc. All rights reserved.

Hypothyroidism (Cont.) Congenital hypothyroidism Hyposecretion of thyroid hormone during youth Low metabolic rate, retarded growth and sexual development, possible mental retardation Copyright © 2017, Elsevier Inc. All rights reserved.

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 Copyright © 2017, Elsevier Inc. All rights reserved.

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 Copyright © 2017, Elsevier Inc. All rights reserved.

Hypothyroidism (Cont.) Common symptoms Thickened skin Hair loss Constipation Lethargy Anorexia Copyright © 2017, Elsevier Inc. All rights reserved.

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 Copyright © 2017, Elsevier Inc. All rights reserved.

Copyright © 2017, Elsevier Inc. All rights reserved. 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 © 2017, Elsevier Inc. All rights reserved.

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. Copyright © 2017, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Copyright © 2017, Elsevier Inc. All rights reserved. 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 Copyright © 2017, Elsevier Inc. All rights reserved.

Copyright © 2017, Elsevier Inc. All rights reserved. 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 Copyright © 2017, Elsevier Inc. All rights reserved.

Copyright © 2017, Elsevier Inc. All rights reserved. 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 © 2017, Elsevier Inc. All rights reserved.

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. Copyright © 2017, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

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 © 2017, Elsevier Inc. All rights reserved.

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 Copyright © 2017, Elsevier Inc. All rights reserved.

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 © 2017, Elsevier Inc. All rights reserved.

Treatment of Hyperthyroidism (Cont.) Antithyroid drugs: thioamide derivatives Methimazole (Tapazole) Propylthiouracil Radioactive iodine (iodine 131) Potassium iodine Copyright © 2017, Elsevier Inc. All rights reserved.

Copyright © 2017, Elsevier Inc. All rights reserved. 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 © 2017, Elsevier Inc. All rights reserved.

Copyright © 2017, Elsevier Inc. All rights reserved. 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. Copyright © 2017, Elsevier Inc. All rights reserved.

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. Copyright © 2017, Elsevier Inc. All rights reserved.

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. Copyright © 2017, Elsevier Inc. All rights reserved.

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. Copyright © 2017, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

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. Copyright © 2017, Elsevier Inc. All rights reserved.

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 Copyright © 2017, Elsevier Inc. All rights reserved.

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). Copyright © 2017, Elsevier Inc. All rights reserved.

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. Copyright © 2017, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

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) Copyright © 2017, Elsevier Inc. All rights reserved.