Chapter 58 Drugs for Thyroid Disorders

Beta blockers for hyperthyroidism

can suppress tachycardia and other symptoms of Graves' disease and is beneficial in a thyrotoxic crisis

Hashimoto's thyroiditis

chronic autoimmune form of thyroiditis, results in hyposecretion of thyroid hormones

Radioactive iodine MOA

destroys thyroid tissue by emission of beta particles

Hypothyroidism's effect during pregnancy

in the 1st trimester it can result in permanent neuropsychological deficits in the child

Synthetic T4 hormone

levothyroxine

Hypothyroidism's effect during infancy

may be permanent or transient; can cause mental retardation and derangement of growth

Thyroid hormones have a profound effect on...

metabolism, cardiac function, growth, and development

What is the first line drug for hyperthyroidism?

methimazole (Tapazole)

The half-life of levothyroxine (Synthroid)

7 days (levels remain steady and only needs to be taken once a day)

Which statements about levothyroxine [Synthroid] are correct? (Select all that apply.) A. Levothyroxine should be taken with food. B. Levothyroxine can be given by IV but is usually taken orally. C. Levothyroxine brands should not be changed if possible. D. Levothyroxine should be taken at night to avoid adverse effects. E. Levothyroxine can affect the metabolism of other medications.

B, C, and E Rationale: Levothyroxine is almost always administered by mouth. Oral doses should be taken once daily on an empty stomach (to enhance absorption). Dosing is usually done in the morning, at least 30 to 60 minutes before breakfast. Maintain patients on the same brand-name levothyroxine product. Intravenous administration is used for myxedema coma and for patients who cannot take levothyroxine orally. Levothyroxine affects the metabolism of other medications, including warfarin.

The nurse instructs a pt about taking levothyroxine (Synthroid). Which statement by the pt indicates the teaching has been effective? A. "To prevent an upset stomach, I will take the drug with food." B. "If I have chest pain or insomnia, I should call my doctor." C. "This medication can be taken with an antacid." D. "The drug should be taken before I go to bed at night."

B. Rationale: Synthroid overdose can cause tachycardia, angina, tremor, nervousness, hyperthermia, and sweating. The pt should contact the prescriber if these symptoms occur. It should be taken in the morning 30-60 minutes before breakfast and should not be taken with antacids because it can reduce the absorption of levothyroxine.

A pt takes levothyroxine 0.75mcg every day. It is most appropriate for the nurse to monitor which lab test to determine whether a dose adjustment is needed? A. thyrotropin-releasing hormone (TRH) B. thyroid-stimulating hormone (TSH) C. serum free T4 test D. sodium iodine level

B. Rationale: TSH is the preferred lab test for monitoring replacement therapy in pts with hypothyroidism

Which finding in a patient taking levothyroxine [Synthroid] and warfarin [Coumadin] would require follow-up by a nurse? A. Cardiac dysrhythmias B. Excessive bruising C. Weight loss of 5 kg D. Shortness of breath

B. excessive bruising Rationale: Levothyroxine intensifies the effect of warfarin, an anticoagulant that increases the patient's risk for bleeding. The warfarin dose may need to be reduced. Bruising, weight loss, and shortness of breath are not effects associated with interactions of levothyroxine and warfarin.

A nurse should consider which diagnostic test a priority to obtain before a patient receives iodine-131? A. White blood cell (WBC) count B. Electrocardiogram (ECG) C. Beta human chorionic gonadotropin (hCG) test (pregnancy hormone test) D. Creatinine level

C. Rationale: Any female patient of reproductive age requires a negative result on a beta hCG (pregnancy hormone) test before iodine-131 (131I) can be administered. 131I is a radioactive isotope used to treat hyperthyroidism and is contraindicated in pregnancy and lactation. A WBC count, ECG, and creatinine level are not indicated before treatment with iodine-131.

Radioactive iodine-131 uses

Graves' disease

2 forms of hyperthyroidism

Graves' disease and toxic nodular goiter (Plummer's disease)

What is the drug of choice for hypothyroidism?

Levothyroxine (Synthroid) (used for all forms)

Synthetic T3 hormone

Liothyronine

Cause of hyperthyroidism

Thyroid-stimulating immunoglobulins (TSIs)

What is the most serious side effect of methimazole (Tapazole)?

agranulocytosis (deficiency of granulocytes in the blood, causing increased vulnerability to infection)

Serum T3 test

can measure the total or free T3 in the body

Serum T4 test

can measure the total or free T4 in the body

levothyroxine drug interactions

drugs that reduce absorption and accelerate metabolism, warfarin (intensifies the effects of W), and catecholamines

What is an indicator of hypothyroidism?

elevated thyroid-stimulating hormone levels

Treatment for thyrotoxic crisis (Thyroid Storm)

high dose potassium iodine or strong iodine solution to suppress hormone production; also sedation, cooling, glucocorticoids, and IV fluids

Signs of thyroid storm

hyperthermia (105F or higher), severe tachycardia, restlessness, agitation, tremor, unconsciousness, coma, hypertension, and heart failure

When should levothyroxine (Synthroid) be taken?

in the morning at least 30-60 minutes before breakfast

methimazole

inhibits the synthesis of thyroid hormones; sole therapy for Graves' disease; can be used as an adjunct medication

Therapeutic strategy for treatment of hypothyroidism in adults

lifelong hormone replacement therapy- levothyroxine (T4) and liothyronine (T3)

Hormone synthesis of the thyroid is stimulated by...

low plasma levels of iodine

Which statement is the most important for a nurse to make to a patient who is taking methimazole? A. "You need to notify your doctor if you have a sore throat and fever." B. "Another medication can be given if you experience any nausea." C. "You may experience some muscle soreness with this medicine." D. "Headache and dizziness may occur but not very frequently."

A. Rationale: Agranulocytosis (the absence of granulocytes to fight infection) is the most serious toxicity associated with methimazole. Sore throat and fever may be the earliest signs. Nausea, muscle soreness, and headache and dizziness are other adverse effects of methimazole that are not as serious as agranulocytosis.

The patient reports that she had to switch pharmacies to save money. She noticed that her "thyroid pill" looks different. The nurse anticipates that the healthcare provider will order what? A. Thyroid-stimulating hormone (TSH) B. Electrocardiogram (ECG) C. Beta human chorionic gonadotropin (hCG) test D. Creatinine level

A. Rationale: If a switch is made (from one branded product to another, from a branded product to a generic product, or from one generic product to another), retest serum TSH in 6 weeks, and adjust the levothyroxine dosage as indicated.

A patient has been given instructions about levothyroxine [Synthroid]. Which statement by the patient indicates an understanding of these instructions? A. "I'll take this medication in the morning so as not to interfere with sleep." B. "I'll plan to double my dose if I gain more than 1 pound per day." C. "It is best to take the medication with food so I don't have any nausea." D. "I'll be glad when I don't have to take this medication in a few months."

A. Rationale: Levothyroxine is used to treat hypothyroidism by increasing the basal metabolism and thus wakefulness. It is administered as a once-daily dose and is a lifelong therapy. It is best taken on an empty stomach to enhance absorption.

Which manifestations should a nurse investigate first when monitoring a patient who is taking levothyroxine [Synthroid]? A. Tachycardia B. Tremors C. Insomnia D. Irritability

A. tachycardia Rationale: High doses of levothyroxine may cause thyrotoxicosis, a condition of profound excessive thyroid activity. Tachycardia is the priority assessment, because it can lead to severe cardiac dysfunction. Tremors, insomnia, and irritability are other symptoms of thyrotoxicosis and should be assessed after tachycardia.

Adverse effects of levothyroxine (Synthroid)

tachycardia, angina, tremors, and can intensify the effects of warfarin (all are rare)

A nurse is caring for a patient with decreased triiodothyronine (T3) and thyroxine (T4) and elevated thyroid-stimulating hormone (TSH) levels. The nurse knows the patient is likely suffering from what? A. Thyrotoxicosis B. Hypothyroidism C. Hyperthyroidism D. Graves' disease

B. hypothyroidism Rationale: The anterior pituitary increases the production of TSH when thyroid hormone levels of T3 and T4 are reduced, reflecting primary hypothyroidism. Patients may experience fatigue caused by a lowered basal metabolic rate. Thyrotoxicosis, hyperthyroidism, and Graves' disease are medical conditions indicative of excessive thyroid activity.

A patient with Graves' disease is treated with iodine-131 therapy. Which statement by the patient would indicate an understanding of the treatment's effects? A. "I'll have to isolate myself from my family so I don't expose them to radiation." B. "I'm looking forward to feeling better immediately after this treatment." C. "I'll tell my doctor if I have fatigue, hair loss, or cold intolerance." D. "I'll need to take this drug on a daily basis for at least 1 year."

C. Rationale: Iodine-131 usually is given as a single treatment to produce remission of Graves' disease. Fatigue, hair loss, and cold intolerance are signs of hypothyroidism, which is a complication of the treatment. Iodine-131 has a quick radioactive decay and half-life; therefore, isolation is not needed, but it can take up to 2 months for the desired response to develop.

Is radioactive iodine indicated in adults and children?

no it is only indicated for adults and is not appropriate for yound children

Clinical presentation of hypothyroidism in adults

pale puffy face, cold dry skin, brittle hair or hair loss, lower HR and temp, lethargy and fatigue, cold intolerance, and impaired mentality

Radioactive iodine is also contraindicated in....

pregnancy and lactation

Thyroid hormones related to growth

promote maturation in infancy and childhood

Causes of thyrotoxic crisis (Thyroid Storm)

pts with thyrotoxicosis who undergo stress, not triggered by hormones, and cannot be identified in lab testing

Congenital hypothyroidism (infancy)

replacement therapy with thyroid hormones

Myxedema (adults)

replacement with thyroid hormones, hypothyroidism during pregnancy, maternal hypothyroidism needs to be diagnosed and treated very early (in most cases treatment needs to be lifelong)

Serum thyroid-stimulating hormone (TSH) test

screening and diagnosis of hypothyroidism

4 applications of methimazole in hyperthyroidism

sole therapy for Graves' disease, adjunct to radiation therapy, suppresses synthesis of hormones before thyroid surgery, and used in thyrotoxic crisis

Action of thyroid hormone

stimulates energy use, stimulates the heart, and promotes growth and development

Treatment of hyperthyroidism

surgical removal of thyroid tissue, destruction of thyroid tissue, suppression of hormone synthesis, beta blockers, and nonradioactive iodine

levothyroxine (Synthroid)

synthetic preparation of thyroid hormone T4

Causes of hypothyroidism in adults

thyroid malfunction, insufficient iodine in the diet, surgical remove of thyroid or destruction with radioactive iodine, and insufficient secretion of TSH and thyropotin-releasing hormone (TRH)

Overdose of levothyroxine can cause...

thyroid toxicosis

Two active hormones produced by the thyroid

triiodothyronine (T3) and thyroxine (T4 tetraiodothyronine)