Chapter 31 Thyroid and Antithyroid drugs

Question 1

The thyroid gland lies across the?

Answer 1

larynx in front of the thyroid cartilage. Its lobes extend laterally on both sides of the front of the neck.

• located close to and communicates with the parathyroid glands, which lie just above and behind it
• parathyroid glands are two pairs of bean-shaped glands. These glands are made up of encapsulated cells that are responsible for maintaining adequate levels of calcium in the extracellular fluid, primarily mobilizing calcium from bone

Question 2

The thyroid gland is responsible for the secretion of three hormones?

Answer 2

essential for the proper regulation of metabolism: thyroxine (T4), triiodothyronine (T3), and calcitonin.

Question 3

T4 and T3 are produced in the thyroid gland; thyroid hormones are made by iodination and coupling with the amino acid tyrosine. The iodide needed for this process is acquired from the diet. When the thyroid gland is signaled to do so, the thyroglobulin–thyroid hormone complex is enzymatically broken down to release T3 and T4 into the circulation. This entire process is triggered by?

Answer 3

thyroid-stimulating hormone (TSH), also called thyrotropin. Its release from the anterior pituitary gland is stimulated when blood levels of T3 and T4 are low.

Question 4

The thyroid hormones:

Answer 4

(1) regulate the basal metabolic rate and lipid and carbohydrate metabolism
(2) are essential for normal growth and development
(3) control the heat-regulating system (thermoregulatory center in the brain), and (4) have various effects on the cardiovascular, endocrine, and neuromuscular systems.

-therefore, hyperfunction or hypofunction of the thyroid gland can lead to a wide range of serious consequences

Question 5

There are three types of hypothyroidism

Answer 5

1) primary
2) Secondary
3) Tertiary

Question 6

Primary hypothyroidism occurs when?

Answer 6

the thyroid gland is not able to perform one of its many functions, such as releasing the thyroid hormones from their storage sites, coupling iodine with tyrosine, trapping iodide, converting iodide to iodine, or any combination of these defects. Primary hypothyroidism is the most common of the three types of hypothyroidism.

Question 7

Secondary hypothyroidism begins at?

Answer 7

the level of the pituitary gland and results from reduced secretion of TSH. TSH is needed to trigger the release of the T3 and T4 stored in the thyroid gland.

Question 8

Tertiary hypothyroidism is caused by a?

Answer 8

reduced level of the thyrotropin-releasing hormone from the hypothalamus. This reduced level, in turn, reduces TSH and thyroid hormone levels.

Question 9

Symptoms of hypothyroidism include?

Answer 9

cold intolerance, unintentional weight gain, depression, dry brittle hair and nails, and fatigue.

Question 10

Hyposecretion of thyroid hormone during youth may lead to?

Answer 10

cretinism, which is characterized by low metabolic rate, retarded growth and sexual development, and possible mental retardation.

Question 11

Hyposecretion of thyroid hormone as an adult may lead to?

Answer 11

myxedema, which is manifested by decreased metabolic rate but also involves loss of mental and physical stamina, weight gain, hair loss, firm edema, and yellow dullness of the skin.

Question 12

Some forms of hypothyroidism may result in the formation of a?

Answer 12

goiter, which is an enlargement of the thyroid gland resulting from its overstimulation by elevated levels of TSH.

• The TSH level is elevated because there is little or no thyroid hormone in the circulation
• certain drugs can cause hypothyroidism, with amiodarone being the most possible. Interestingly, amiodarone can also cause hyperthyroidsim

Question 13

Hyperthyroidism is caused by?

Answer 13

excessive secretion of thyroid hormone by the thyroid gland and may be caused by different diseases. Always assess and document important information about the patient’s medical history appropriately.

• Diseases known to cause hyperthyroidism include: Grave’s disease, Plummer’s disease (toxic nodular disease)
• thyroid storm is a severe and potentially life-threatening exacerbation of the symptoms of hyperthyroidism that is usually induced by stress or infection
• Hyperthyroidism can affect multiple body systems, resulting in an overall increase in metabolism. Commonly reported symptoms are diarrhea, flushing, increased appetite, muscle weakness, fatigue, palpitations, irritability, nervousness, sleep disorders, heat intolerance, and altered menstrual flow.

Question 14

Thyroid hormone replacement is generally carried out carefully by the prescriber with frequent monitoring of?

Answer 14

serum levels until stabilization appears to have occurred. Monitor and review laboratory values to be sure that serum levels are within normal limits to avoid possible toxicity.

Question 15

Thyroid hormone replacement drugs can be either natural or synthetic in origin. The natural thyroid preparations are derived from?

Answer 15

• natural thyroid preparations: derived from thyroid glands of animals such as cattle and hogs. Currently only one natural thyroid replacement preparation is available in the United States, and it is called simply thyroid or thyroid, desiccated.
• desiccation is the term for the drying process used to prepare this drug form
• all natural preparations are standardized for their iodine content

Question 16

Thyroid hormone replacement drugs can be either natural or synthetic in origin. The synthetic thyroid preparations are?

Answer 16

Levothyroxine (T4), liothyronine (T3), & liotrix (which contains a combination of T4 and T3 in a 4:1 ratio)

Question 17

Monitoring of serum TSH and free thyroid hormone levels is required to determine the?

Answer 17

appropriate dose of thyroid replacement drugs.

Question 18

Thyroid hormone replacement is generally carried out carefully by the prescriber with frequent monitoring of serum levels until?

Answer 18

stabilization appears to have occurred. Monitor and review laboratory values to be sure that serum levels are within normal limits to avoid possible toxicity.

Question 19

Thyroid hormone replacement drugs can be either natural or synthetic in origin. The natural thyroid preparations are derived from?

Answer 19

thyroid glands of animals such as cattle and hogs.

Question 20

Currently only one natural thyroid replacement preparation is available in the United States, and it is called simply?

Answer 20

thyroid or thyroid, desiccated.

Question 21

What is required to determine the appropriate dose of thyroid replacement drugs.

Answer 21

Monitoring of serum TSH and free thyroid hormone levels

Question 22

Thyroid replacement drugs mechanism of action

Answer 22

At the cellular level, thyroid drugs work to induce changes in the metabolic rate, including the rate of protein, carbohydrate, and lipid metabolism, and to increase oxygen consumption, body temperature, blood volume, and overall cellular growth and differentiation. They also stimulate the cardiovascular system by increasing the number of myocardial beta-adrenergic receptors. This, in turn, increases the sensitivity of the heart to catecholamines and ultimately increases cardiac output. In addition, thyroid hormones increase renal blood flow and the glomerular filtration rate, which results in a diuretic effect.

Question 23

Thyroid replacement drugs indications

Answer 23

Thyroid drugs can also be used for the diagnosis of suspected hyperthyroidism (as in a TSH-suppression test) and in the prevention or treatment of various types of goiters. They are also used for 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.

Question 24

Thyroid replacement drugs contraindications

Answer 24

• known drug allergy
• recent myocardial infarction
• adrenal insufficiency
• hyperthyroidism

Question 25

Thyroid replacement drugs Adverse effects

Answer 25

Usually result of overdose

-cardiac dysrhythmia with risk of life-threatening or fatal irregularities

Question 26

Hypothyroidism during pregnancy is treated with dosage

adjustments every?

Answer 26

4 weeks to maintain the TSH level at the lower end of the normal range.

Question 27

Thyroid replacement drugs interactions

Answer 27

• may enhance activity of oral anticoagulants, the dosages of which may need to be reduced
• Taking concurrently with digitalis glycosides may decrease serum digitalis levels
• Cholestyramine binds to thyroid hormone in the gastrointestinal tract, which possibly reduces the absorption of both drugs
• Diabetic patients taking a thyroid drug may require increased dosages of their hypoglycemic drugs.

Question 28

Thyroid replacement drug: Levothyroxine (Synthroid)

Answer 28

• one advantage over natural thyroid preparations is that it is chemically pure, being 100% T4 (Thyroxine); this makes its effects more predictable than other thyroid preparations
• half life is long enough that is only needs to be administered once a day
• available in oral and parenteral form
• Pregnancy A
• switching between different brands of levothyroxine during Tx can destabilize the course of Tx. Thyroid function test results need to be monitored carefully when switching products
• dosed in micrograms
• common medication error is to write intended dose in milligrams instead of micrograms (error results in thousand fold overdose)
• doses higher than 200 mcg need to be questioned
• available in IV form which is 50% of oral dose

Question 29

Care must be taken when preparing IV doses of levothyroxine for infusions. It is essential to remember that the?

Answer 29

vial must be diluted FIRST, and then the dose is calculated based on the concentration of the reconstituted medication, not the size of the vial.

Question 30

For levothyroxine (Synthroid, Levothroid, and Levoxyl), the pharmacokinetic characteristics include an onset of action of?

Answer 30

3 to 5 days, peak plasma concentrations within 24 hours,
elimination half-life of 6 to 10 days, and a duration of action of 24 hours. Due to the prolonged half-life of this drug, there is an increased risk of toxicity.

Question 31

Other adverse effects associated with thyroid drugs include?

Answer 31

tachycardia, palpitations, angina, dysrhythmias, hypertension, insomnia, tremors, headache, anxiety, nausea, diarrhea, cramps, menstrual irregularities, weight loss, sweating, fever, and heat intolerance.

Question 32

Toxicity of thyroid drugs is manifested by the following

Answer 32

weight loss, tachycardia, nervousness, tremors, hypertension, headache, insomnia, menstrual irregularities, and cardiac irregularities or palpitations.

Question 33

Another important pharmacokinetic property of thyroid drugs is that the drug is protein bound. A highly protein-bound drug acts like a?

Answer 33

biologic sustained-release drug and remains in the body
longer, with increased risk of more interactions with other
highly protein-bound drugs as well as greater potential for toxicity.

Question 34

Patients receiving levothyroxine need to report the occurrence of?

Answer 34

excitability, irritability, or palpitations to the prescriber
because these symptoms may indicate toxicity.

Question 35

Nursing Process for thyroid drugs

Answer 35

• Assess levels of T3, T4, and TSH before and during drug therapy
• Review baseline vital signs w/increased attention to history of cardiac dysrhythmias because of possible adverse effects of cardiac irregularities that may be life threatening.
• For female patient, perform thorough assessment of reproductive system due to impact of thyroid hormones on system.
• Lifespan considerations include increased sensitivity to the effects of thyroid medications in elderly patients
• certain thyroid drugs work faster than others due to dosage form and properties
• Drug interactions with: oral anticoagulants (increased activity of oral anticoagulants), digitalis glycosides (decrease in digitalis levels), cholestyramine, and oral hypoglycemic drugs
• if pt is taking oral anticoagulant, monitor blood levels of anticoagulant closely
• individualization of drug therapy important

Question 36

Nursing implementation for thyroid drugs

Answer 36

• When thyroid drugs are administered, it is important that the drug be given at the same time every day to help maintain consistent blood levels of the drug
• Emphasize to the patient that it is best to administer thyroid drugs once daily in the morning, if possible, to decrease the likelihood of insomnia, which may result from evening dosing and the subsequent increase in energy level
• take in the morning and on an empty stomach at least 30 min before breakfast
• avoid taking thyroid replacement drug with vitamins or supplements containing iron and/or calcium within a 4 hour time frame
• avoid antacids and OTC preparations with iodine
• avoid iodized salt and iodine-rich foods: soybeans, tofu, turnips, high-iodine seafood, some breads
• avoid interchanging brands
• may crush tablets
• if pt is scheduled to undergo radioactive iodine isotope studies, the thyroid replacement drug is discontinued about 4 weeks before the test
• older adults may require alteration of dosage amount, with a decrease of up to 25%

Question 37

Therapeutic response to thyroid replacement drugs is manifested by

Answer 37

Disappearance of symptoms of hypothyroidism; improved energy levels as well as improved mental and physical stamina

Question 38

Thyroid drugs patient education

Answer 38

• taken 1/2 to 1 hour BEFORE breakfast on empty stomach to enhance absorption & maintain consistent hormonal levels
• sleeplessness prevented by taking in the morning
• do not abruptly discontinue. Life long therapy is norm
• keep follow up appts: monitor thyroid hormone levels, CBCs, results of liver function studies
• brands cannot be interchanged
• do NOT take at same time with vitamins/supplements
• take w/6-8 oz of water
• immediately report: chest pain, weight loss, palpitations, tremors, sweating, neurvousness, SOB, insomnia. May indicate toxicity
• keep daily journal
• may take several weeks to see therapeutic effects
• protect tablet from light
• do not take OTC medications

Question 39

Signs and symptoms associated with hypothyroidism include?

Answer 39

Myxedema with decreased metabolic decreased metabolic rate, loss of mental/physical stamina, weight gain, hair loss, firm edema, yellow dullness of skin

Question 40

Signs and symptoms of hyperthyroidism include?

Answer 40

increased metabolic rate, diarrhea, flushing, increased appetite, muscle weakness, fatigue, palpitations, irritability, nervousness, sleep disorders, heat intolerance, altered menstrual flow

Question 41

Treatment of hyperthyroidism is aimed at treating either the primary cause or the symptoms of the disease.

Answer 41

Antithyroid drugs, iodides, ionic inhibitors, surgery, and radioactive isotopes of iodine are used to treat the underlying cause, and drugs such as beta blockers are used to treat the symptoms.

Question 42

Radioactive iodine works by?

Answer 42

destroying the thyroid gland, in a process known as ablation, emitting destructive beta rays once it is taken up into the follicles of the thyroid gland. It is a commonly used treatment for both hyperthyroidism and thyroid
cancer.

Question 43

Antithyroid drugs mechanism of action

Answer 43

Propylthiouracil acts by inhibiting the incorporation of iodine molecules into the amino acid tyrosine, a process required to make the precursors of T3 and T4. By doing so these drugs impede the formation of thyroid hormone

• propylthiocuracil has added ability to inhibit conversion of T4 to T3 in the peripheral circulation
• they can’t inactivate already existing thyroid hormone

Question 44

Antithyroid drugs indications: Surgical resection of the thyroid gland (thyroidectomy) involves removal of part or all of the thyroid gland. It is usually a very effective way to treat hyperthyroidism, but?

Answer 44

lifelong hormone replacement therapy is normally required after thyroid surgery. It is often used both in patients who are intolerant of antithyroid drug therapy and in pregnant women.

Question 45

Antithyroid drugs contraindications

Answer 45

• known drug allergy
• use in pregnancy controversial
• propylthiouracil used during first trimester ONLY, then methimazole used for remainder
• pregnancy D

Question 46

Antithyroid drugs adverse effects

Answer 46

liver and bone marrow toxicity

Question 47

Antithyroid drugs interactions

Answer 47

-additive leukopenic effects when taken in conjunction with other bone marrow suppressants and an increase in the activity of oral anticoagulants

Question 48

Antithyroid drug: Propylthiouracil (PTU)

Answer 48

A thioamide antithyroid drugs classified as a pregnancy D

• 2 weeks of therapy with this drug may be necessary before symptoms improve
• ONLY oral form as a 50-mg tablet

Question 49

Nursing assessment for antithyroid drugs

Answer 49

• assess vital signs and s/s for thyroid crisis (thyroid storm)
• thyroid storm manifested as exacerbation of hyperthyroid symptoms and potentially life-threatening
• asses for thyroid storm means assessing for precipitating causes, such as stress or infection
• drug interactions: oral anticoagulants (increase in anticoagulation and thus risk for bleeding), medications that may lead to bone marrow suppression or cause leukopenia (antithyroid drugs may cause additive effects or worsening of bone marrow suppression)

Question 50

Antithyroid drugs implementation

Answer 50

-when taking propylthiouracil dose with meals to decrease stomach upset
-report: fever, sore throat, mouth ulcers or sores, skin eruptions, unusual bleeding or bruising. May indicate problems of liver toxicity and/or bone marrow toxicity with possible leukopenia
-monitor liver function tests & CBC
-avoid iodized salt or eating shellfish because of potential for altering drugs effectiveness
-

Question 51

Antithyroid drugs implementation

Answer 51

• when taking propylthiouracil dose with meals to decrease stomach upset
• report: fever, sore throat, mouth ulcers or sores, skin eruptions, unusual bleeding or bruising. May indicate problems of liver toxicity and/or bone marrow toxicity with possible leukopenia
• monitor liver function tests & CBC
• avoid iodized salt or eating shellfish because of potential for altering drugs effectiveness
• be aware of s/s of hypothyroidism: unexplained weight gain, loss of mental and physical stamina, hair loss, firm edema, and yellow dullness of the skin (indicative of myxedema or a decrease in metabolic rate). If these occur, report immediately to prescriber
• Frequently monitor CBCs to watch for potential problems with leukopenia. It is also important to monitor the results of liver function studies.

Question 52

Adverse effects associated with antithyroid drugs include?

Answer 52

drowsiness, headache, vertigo, nausea, vomiting, diarrhea, loss of taste, bleeding, leukopenia, rash, myalgia, and arthralgia.

Question 53

A therapeutic response to antithyroid medications includes a?

Answer 53

return to normal status with little to no evidence of hyperthyroid. Adverse effects include the possibility of leukopenia, which may be manifested by fever, sore throat, lesions, or other signs of infection.

Question 54

Signs and symptoms of hyperthyroidism include

Answer 54

Increased metabolic rate, diarrhea, flushing, increased appetite, muscle weakness, fatigue, palpitations, irritability, nervousness, sleep disorders, heat intolerance, altered menstrual flow

Question 55

Advise patients taking antithyroid medications that they are better tolerated with?

Answer 55

When taken with meals or a snack. They must also be given at the same time everyday to maintain consistent blood levels with this drug

• Never withdrawn abruptly
• do NOT take with any OTC
• Avoid eating foods high in iodine, such as tofu and other soy products, turnips, seafood, iodized salt, and some breads. These foods may interfere with the effectiveness of the antithyroid drug