Hypothyroidism - Management of Patients With Thyroid Disorders

HYPOTHYROIDISM

Hypothyroidism results from suboptimal levels of thyroid hor-mone. Thyroid deficiency can affect all body functions and can range from mild, subclinical forms to myxedema, an advanced form. The most common cause of hypothyroidism in adults is autoimmune thyroiditis (Hashimoto’s disease), in which the immune system attacks the thyroid gland. 

Symptoms of hyper thyroidism may later be followed by those of hypothyroidism and myxedema. Hypothyroidism also commonly occurs in patients with previous hyperthyroidism who have been treated with radio-iodine or antithyroid medications or who have had surgery. It oc-curs most frequently in older women. Radiation therapy for head and neck cancer can also cause hypothyroidism in older men; therefore, testing of thyroid function is recommended for all pa-tients who receive such treatment. Other causes of hypothyroid-ism are presented in Chart 42-2.

Pathophysiology

More than 95% of patients with hypothyroidism have primary or thyroidal hypothyroidism, which refers to dysfunction of the thyroid gland itself. When thyroid dysfunction is caused by fail-ure of the pituitary gland, the hypothalamus, or both, it is known as central hypothyroidism. It may be referred to as pituitary or secondary hypothyroidism if it is caused entirely by a pituitary disorder, and hypothalamic or tertiary hypothyroidism if it is at-tributable to a disorder of the hypothalamus resulting in inade-quate secretion of TSH because of decreased stimulation by TRH. When thyroid deficiency is present at birth, the condition is known as cretinism. In such instances, the mother may also suffer from thyroid deficiency.

The term myxedema refers to the accumulation of mucopoly-saccharides in subcutaneous and other interstitial tissues. Al-though myxedema occurs in long-standing hypothyroidism, the term is used appropriately only to describe the extreme symptoms of severe hypothyroidism.

Clinical Manifestations

Early symptoms of hypothyroidism are nonspecific, but extreme fatigue makes it difficult for the person to complete a full day’s work or participate in usual activities. Reports of hair loss, brittle nails, and dry skin are common, and numbness and tingling of the fingers may occur. On occasion, the voice may become husky, and the patient may complain of hoarseness. Menstrual disturbances such as menorrhagia or amenorrhea occur, in addition to loss of libido. Hypothyroidism affects women five times more frequently than men and occurs most often between 30 and 60 years of age.

Severe hypothyroidism results in a subnormal temperature and pulse rate. The patient usually begins to gain weight even without an increase in food intake, although severely hypothyroid patients may be cachectic. The skin becomes thickened because of an accumulation of mucopolysaccharides in the subcutaneous tissues (the origin of the term myxedema). The hair thins and falls out; the face becomes expressionless and masklike. The patient often complains of being cold even in a warm environment.

At first, the patient may be irritable and may complain of fa-tigue, but as the condition progresses, the emotional responses are subdued. The mental processes become dulled, and the patient appears apathetic. Speech is slow, the tongue enlarges, and hands and feet increase in size. The patient frequently complains of con-stipation. Deafness may also occur.

Advanced hypothyroidism may produce personality and cog-nitive changes characteristic of dementia. Inadequate ventilation and sleep apnea can occur with severe hypothyroidism. Pleural ef-fusion, pericardial effusion, and respiratory muscle weakness may also occur.

Severe hypothyroidism is associated with an elevated serum cholesterol level, atherosclerosis, coronary artery disease, and poor left ventricular function. The patient with advanced hypo-thyroidism is hypothermic and abnormally sensitive to sedatives, opioids, and anesthetic agents. Therefore, these medications are administered only with extreme caution.

Patients with unrecognized hypothyroidism who are under-going surgery are at increased risk for intraoperative hypotension and postoperative heart failure and altered mental status.

Myxedema coma describes the most extreme, severe stage of hypothyroidism, in which the patient is hypothermic and un-conscious. Myxedema coma may follow increasing lethargy, pro-gressing to stupor and then coma. Undiagnosed hypothyroidism may be precipitated by infection or other systemic disease or by use of sedatives or opioid analgesic agents. The patient’s respira-tory drive is depressed, resulting in alveolar hypoventilation, pro-gressive CO₂ retention, narcosis, and coma. These symptoms, along with cardiovascular collapse and shock, require aggressive and intensive therapy if the patient is to survive. Even with early vigorous therapy, however, mortality is high.

Gerontologic Considerations

Most patients with primary hypothyroidism are 40 to 70 years of age and present with long-standing mild to moderate hypothy-roidism. Subclinical disease is common among older women and can be asymptomatic or mistaken for other medical conditions. Subtle symptoms of hypothyroidism, such as fatigue, muscle aches, and mental confusion, may be attributed to the normal aging pro-cess by the patient, family, and health care provider. The higher prevalence of hypothyroidism in elderly people may be related to alterations in immune function with age. Regular screening of TSH levels is recommended for people older than 60 because they are at high risk for hypothyroidism (Ladenson et al., 2000).

The signs and symptoms of hypothyroidism are often atypi-cal in elderly people; the elderly patient may have few or no symp-toms until the dysfunction is severe. Depression, apathy, or decreased mobility or activity may be the major initial symptom. The major symptoms of hypothyroidism may be depression and apathy, and may be accompanied by significant weight loss. One fourth of affected elderly patients experience constipation

Medical Management

The primary objective in the management of hypothyroidism is to restore a normal metabolic state by replacing the missing hormone.

PHARMACOLOGIC THERAPY

Synthetic levothyroxine (Synthroid or Levothroid) is the pre-ferred preparation for treating hypothyroidism and suppressing nontoxic goiters. The dosage for hormone replacement is based on the patient’s serum TSH concentration. Desiccated thyroid is used less frequently because it often results in transient elevated serum concentrations of T₃, with occasional symptoms of hyper-thyroidism. If replacement therapy is adequate, the symptoms of myxedema disappear and normal metabolic activity is resumed.

Prevention of Cardiac Dysfunction. 

Any patient who has hadhypothyroidism for a long period is almost certain to have ele-vated serum cholesterol levels, atherosclerosis, and coronary artery disease. As long as metabolism is subnormal and the tissues, including the myocardium, require relatively little oxygen, a re-duction in blood supply is tolerated without overt symptoms of coronary artery disease. When thyroid hormone is administered, however, the oxygen demand increases, but oxygen delivery can-not be increased unless, or until, the atherosclerosis improves. This occurs very slowly, if at all. The occurrence of angina is the signal that the oxygen needs of the myocardium exceed its blood supply. Angina or dysrhythmias may occur when thyroid replace-ment is initiated because thyroid hormones enhance the cardio-vascular effects of catecholamines.

Obviously, if angina or dysrhythmias occur, thyroid hormone administration must be discontinued immediately. Later, when it can be resumed safely, thyroid hormone replacement should be prescribed cautiously at a lower dosage and under the close ob-servation of the physician and the nurse.

Prevention of Medication Interactions. 

Precautions must be takenduring the course of therapy because of the interaction of thyroid hormones with other medications. Thyroid hormones may in-crease blood glucose levels, which may necessitate adjustment in the dosage of insulin or oral antidiabetic agents in patients with di-abetes. The effects of thyroid hormone may be increased by phenytoin (Dilantin) and tricyclic antidepressant agents. Thyroid hormones may also increase the pharmacologic effects of digitalis glycosides, anticoagulant agents, and indomethacin, requiring careful observation and assessment by the nurse for side effects. Bone loss and osteoporosis may also occur with thyroid therapy.

Even in small doses, hypnotic and sedative agents may induce profound somnolence, lasting far longer than anticipated. Moreover, they are likely to cause respiratory depression, which can easily be fatal because of decreased respiratory reserve and alveo-lar hypoventilation. If their use is necessary, the dose is one-half or one-third that ordinarily prescribed in patients of similar age and weight with normal thyroid function. If these medications must be used, the patient must be monitored closely for signs of impending narcosis (stupor-like condition) or respiratory failure.

Gerontologic Considerations

In the elderly patient with mild to moderate hypothyroidism, thyroid hormone replacement must be started with low dosages and increased gradually to prevent serious cardiovascular and neurologic side effects. Angina, for example, may occur with rapid thyroid replacement in the presence of coronary artery disease secondary to the hypothyroid state. Heart failure and tachydys-rhythmias may worsen during the transition from the hypothy-roid state to the normal metabolic state. Dementia may become more apparent during early thyroid hormone replacement in the elderly patient.

Elderly patients with severe hypothyroidism and atheroscle-rosis may also become confused and agitated if their metabolic rates are raised too quickly. Marked clinical improvement follows the administration of hormone replacement; such medication must be continued for life, even though signs of hypothyroidism disappear within 3 to 12 weeks.

Myxedema and myxedema coma generally occur exclusively in patients older than 50 years. The high mortality rate of myxedema coma mandates immediate intravenous administration of high doses of thyroid hormone as well as supportive care.

SUPPORTIVE THERAPY

In severe hypothyroidism and myxedema coma, management includes maintaining vital functions. Arterial blood gases may be measured to determine CO₂ retention and to guide the use of assisted ventilation to combat hypoventilation. Pulse oximetry may also be helpful in monitoring oxygen saturation levels. Fluids are administered cautiously because of the danger of water intox-ication. Application of external heat (eg, heating pads) is avoided because it increases oxygen requirements and may lead to vas-cular collapse. If hypoglycemia is evident, concentrated glucose may be prescribed to provide glucose without precipitating fluid overload. Thyroid hormone (usually Synthroid) is administered intravenously until consciousness is restored if myxedema has progressed to myxedema coma. The patient is then continued on oral thyroid hormone therapy. Because of an associated adreno-cortical insufficiency, corticosteroid therapy may be necessary.

Nursing Management

Nursing care of the patient with hypothyroidism and myxedema is summarized in the Plan of Nursing Care.

MODIFYING ACTIVITY

The patient with hypothyroidism experiences decreased energy and moderate to severe lethargy. As a result, the risk for compli-cations from immobility increases. The patient’s ability to exer-cise and participate in activities is further limited by the changes in cardiovascular and pulmonary status secondary to hypothy-roidism. A major role of the nurse is assisting with care and hygiene while encouraging the patient to participate in activities within established tolerance levels to prevent the complications of immobility.

MONITORING PHYSICAL STATUS

The nurse closely monitors the patient’s vital signs and cognitive level to detect the following:

·      Deterioration of physical and mental status

·      Signs and symptoms indicating that treatment has resulted in the metabolic rate exceeding the ability of the cardio-vascular and pulmonary systems to respond

·      Continued limitations or complications of myxedema

PROMOTING PHYSICAL COMFORT

The patient often experiences chilling and extreme intolerance to cold, even if the room feels comfortable or hot to others. Extra clothing and blankets are provided, and the patient is protected from drafts. Use of heating pads and electric blankets is avoided because of the risk of peripheral vasodilation, further loss of body heat, and vascular collapse. Additionally, the patient could be burned by these items without being aware of it because of de-layed responses and decreased mental status.

PROVIDING EMOTIONAL SUPPORT

The patient with moderate to severe hypothyroidism may expe-rience severe emotional reactions to changes in appearance and body image and the frequent delay in diagnosis. The nonspecific, early symptoms may produce negative reactions by family mem-bers and friends, and the family and friends may have labeled the patient mentally unstable, uncooperative, or unwilling to partic-ipate in self-care activities.

As hypothyroidism is treated successfully and symptoms subside, the patient may experience depression and guilt as a re-sult of the progression and severity of symptoms that occurred. The nurse informs the patient and family that the symptoms and inability to recognize them are common and part of the dis-order itself. The patient and family may require assistance and counseling to deal with the emotional concerns and reactions that result.

PROMOTING HOME AND COMMUNITY-BASED CARE

Teaching Patients Self-Care. 

Because most hypothyroidism treat-ment takes place at home, the patient and family require infor-mation and instruction that will enable them to monitor the patient’s condition and response to therapy. The nurse instructs the patient about the desired actions and side effects of medications and about how and when to take prescribed medications. The importance of continuing to take medications as prescribed even after symptoms improve is stressed to the patient. Because of the slowed mental processes that occur with hypothyroidism, it is im-portant that a family member also be informed and instructed about treatment goals, medication schedules, and side effects to be reported to the physician. The nurse provides written instruc-tions and guidelines for the patient and family.

Dietary instruction is provided to promote weight loss once medication has been initiated and to promote return of normal bowel patterns. The patient and family are often very concerned about the changes they have observed as a result of the hypothy-roid state. It is often reassuring to the patient and family to be in-formed that many of the symptoms will disappear with effective treatment (Chart 42-3).

Continuing Care. 

The patient with hypothyroidism and myx-edema coma needs considerable follow-up and health care. Be-fore hospital discharge, arrangements are made to ensure that the patient returns to an environment that will promote adherence to the prescribed treatment plan. Assistance in devising a sched-ule or record ensures accurate and complete administration of medications. The nurse reinforces the importance of continued thyroid hormone replacement and periodic follow-up testing and instructs the patient and family members about the signs of over-medication and undermedication.

If indicated, a referral is made for home care. The home care nurse assesses the patient’s progress toward recovery and ability to cope with the recent changes, along with the patient’s physical and cognitive status and the patient’s and family’s understanding of the importance of prescribed long-term medication therapy and compliance with the medication schedule and recommended follow-up tests and appointments. The nurse documents, and re-ports to the patient’s primary health care provider, subtle signs and symptoms that may indicate either inadequate or excessive thyroxine hormone.

Gerontologic Considerations

The elderly patient requires periodic follow-up monitoring of serum TSH levels because poor compliance with therapy may occur or the patient may take the medications erratically. A careful history may identify the need for further teaching about the im-portance of the medication. Because of the prevalence of hypothy-roidism, testing of serum TSH levels in elderly people every 5 years has been recommended (Smallridge, 2000). In addition, the pa-tient is reminded of the importance of participating in general health promotion activities and recommended health screening.