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LEARNING OBJECTIVES

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LEARNING OBJECTIVES

Upon completion of the chapter, the reader will be able to:

  1. Discuss the prevalence of common thyroid disorders, including mild and overt hypothyroidism and hyperthyroidism.

  2. Explain the major components of the hypothalamic–pituitary–thyroid axis and interaction among these components.

  3. Discuss the relationship between serum thyroid-stimulating hormone (TSH) levels and primary thyroid disease, and the advantages for use of TSH levels over other tests such as serum T4 (thyroxine) and T3 (triiodothyronine) levels.

  4. Identify typical signs and symptoms of hypothyroidism and the consequences of suboptimal treatment.

  5. Describe clinical use of levothyroxine (LT4) in the treatment of hypothyroidism.

  6. Discuss the issues regarding LT4 product bioequivalence and reasons for maintaining patients on the same product.

  7. Describe the management of hypothyroidism and hyperthyroidism in pregnant women.

  8. Identify typical signs and symptoms of Graves disease and consequences of inadequate treatment.

  9. Discuss the pharmacotherapy of Graves disease, including advantages and disadvantages of antithyroid drugs versus radioactive iodine, adverse effects, and patient monitoring.

  10. Describe the potential effects of selected drugs, including amiodarone, lithium, interferon-α, and tyrosine kinase inhibitors (TKIs) on thyroid function.

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INTRODUCTION

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Thyroid disorders are common. More than 2 billion people, or 38% of the world’s population, have iodine deficiency, resulting in 74 million people with goiter. Although overt iodine deficiency is not a significant problem in developed countries, a number of common thyroid conditions exist. The most common are hypothyroidism and hyperthyroidism, which often require long-term pharmacotherapy. Undetected or improperly treated thyroid disease can result in long-term adverse sequelae, including increased mortality. It is important that clinicians are aware of the prevalence of thyroid disorders, methods of identifying thyroid disorders, and appropriate therapy. This chapter focuses on the most common pharmacologically treated thyroid disorders.

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EPIDEMIOLOGY

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Among 4392 people 12 years of age and older in a sample representing the geographic and ethnic distribution of the US population, hypothyroidism was found in 3.7% (3.4% mild) and hyperthyroidism in 0.5%.1 The prevalence of hypothyroidism correlated with age and was higher in older age groups, whites, and Hispanics, but was lower in blacks. Compared with the total population, people aged 50 to 79 years had an almost twofold higher prevalence, and those aged 80 years and older had a fivefold higher prevalence. Pregnant women also had a higher prevalence of hypothyroidism than nonpregnant women across all races and ethnicities. The Colorado Thyroid Health Survey assessed thyroid function in 25,862 subjects attending a health fair.2 Overall prevalence of an abnormal thyroid-stimulating hormone (TSH; thyrotropin) level was 11.7% of the study population, with 9.4% hypothyroid (9% subclinical) and 2.2% hyperthyroid (2.1% subclinical). Of the 916 subjects taking thyroid medication, 60% were euthyroid (had normal thyroid function or hormone activity), with an equal distribution between subclinical hypothyroidism and hyperthyroidism. The National Health and Nutrition Examination Survey (NHANES) study also found that many patients receiving thyroid medications had an abnormal ...

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