Thyroid Dysfunction _________________________________________________________________________
A routine screening, even in the absence of symptoms, may indicate an enlarged thyroid gland (on palpation) or labora- tory blood testing may reveal abnormal results. The most specific test for the diagnosis of Hashimoto thyroiditis is a blood test to detect the presence of antibodies against thyroid peroxidase, an essential thyroid enzyme. There are some cases of the disease for which the blood tests are normal. In patients with Hashimoto thyroiditis, the TSH or thyrotropin test will have an increased level, indicating hypothyroidism. The TSH rises markedly when the thyroid gland has even a small underproduction of thyroid hormone. The free T4 level may be low if there is a deficiency of thyroid hormone in the blood. Additionally, fine-needle aspiration of a nodule may be done as part of the diagnostic work-up for Hashimoto thyroiditis to exclude malignancy or the presence of a thyroid lymphoma in fast-growing thyroid goiters [7; 19] . Several treatment options are available to assist patients with Hashimoto thyroiditis. Thyroid hormone therapy with levo- thyroxine sodium is the treatment of choice, particularly with those who have a goiter. It is usually necessary to treat this disease for a lifetime [7; 18; 19] . Myxedema Myxedema is a rare, and frequently fatal, complication of hypothyroidism. It is seen most often in patients who have undiagnosed or untreated hypothyroidism. When patients with uncontrolled hypothyroidism are subjected to stress (e.g., infection, trauma, surgery, heart disease, seizures), they may develop full-blown myxedema or myxedema coma. Symp- toms of this condition include facial and periorbital edema, thickened tongue, blank facial expression, and slowing of all motor activities. There are decreased respirations and possible respiratory acidosis. Vital signs show bradycardia, hypothermia, and a decrease in blood pressure; heart failure is a concern. It is important to begin treatment as soon as possible, as coma and death can occur. Treatment consists of intravenous levothyroxine with glucose and corticosteroids. Nursing man- agement includes monitoring vital signs and urinary output, and close attention should be paid to the skin, as edema may cause tissue breakdown. Blankets may be necessary to combat a low body temperature. Because treatment includes thyroid supplements, it is important to be on the alert for manifesta- tions of thyrotoxicosis, such as tachycardia, sweating, agitation, tremor, and palpitations [14; 21] . HYPERTHYROIDISM Less common than hypothyroidism, but still problematic, is hyperthyroidism. This condition is characterized by overactivity of the thyroid gland, whereby the thyroid gland produces an excess of the hormone T4. As discussed, the rate by which T4 and T3 are released is controlled by the hypothalamus and the pituitary gland. The hypothalamus signals the pituitary gland to make TSH, which in turn stimulates increased production of thyroid hormone.
There are several known causes of hyperthyroidism. In 60% to 80% of cases, the autoimmune disorder Graves disease is the source of the dysfunction. Other possible causes include toxic multinodular goiter (15% to 20% of cases), toxic adenoma (3% to 5% of cases), thyroiditis (inflammation of the thyroid gland), or overdosing of thyroid replacement hormone in the treatment of hypothyroidism [7; 22] . SIGNS AND SYMPTOMS There are several observable signs that indicate the possibility of hyperthyroidism in the patient. Respiratory system manifes- tations include shortness of breath and increased respiratory rate and depth. Cardiovascular system changes are typically seen with a rapid, bounding pulse and/or palpitations. In addi- tion to an increased heart rate, there may also be an increased cardiac output with possible congestive heart failure and accompanying edema. Typically, both the systolic and diastolic blood pressures are elevated 10–15 mm Hg above the patient’s known normal levels. The fluid retention and decreased uri- nary output that occur in patients with hypothyroidism may also be seen in patients with hyperthyroidism [22; 23] . Musculoskeletal system manifestations include poor coor- dination (secondary to tremors), muscle weakness, fatigue, and proximal muscle wasting. The disease may also affect the gastrointestinal system, with increased appetite secondary to increased peristalsis, diarrhea, and weight loss. There is accompanying vomiting with abdominal pain that can lead to malnutrition and a negative nitrogen balance [22; 23] . Nervousness, anxiety, and emotional instability are frequently seen and may be accompanied by tremors. Patients may also develop heat intolerance, warm skin, and profuse sweating. Hair loss is a common complication [22; 23] . Hyperthyroidism can also have adverse effects on patients’ reproductive abilities. Women can experience decreased fertil- ity, amenorrhea, or irregular periods. Hyperthyroidism is also correlated with an increased risk for spontaneous abortion [22; 23]. As with hypothyroidism, men may develop impotence and decreased libido. Exophthalmos (i.e., abnormal protrusion of the eyeball) is a frequent manifestation and is often the first sign of a thyroid imbalance. This condition will be described in greater detail later in this course. Some patients, particularly older individuals, may have very subtle signs or symptoms, if any are present at all. The most commonly experienced symptoms in all patients are increased heart rate, heat intolerance, and fatigue. Beta blockers have also been known to mask many of the signs of hyperthyroid- ism [23; 24] .
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