49 Hypothyroidism
Overview/pathophysiology
Hypothyroidism is a condition in which there is an inadequate amount of circulating thyroid hormone, causing a decrease in metabolic rate that affects all body systems.
Primary hypothyroidism accounts for 90% of cases of hypothyroidism and is caused by pathologic changes in the thyroid itself. The most common cause of the disease in the United States is chronic autoimmune thyroiditis (Hashimoto’s disease). Postpartum thyroiditis and granulomatous thyroiditis related to inflammatory conditions or viral syndromes also occur.
Secondary hypothyroidism is caused by dysfunction of the anterior pituitary gland, which results in decreased release of thyroid-stimulating hormone (TSH). Tertiary hypothyroidism is caused by a hypothalamic deficiency in the release of thyrotropin-releasing hormone (TRH).
When hypothyroidism is untreated, or when a stressor such as infection affects an individual with hypothyroidism, a life-threatening condition known as myxedema coma can occur. Hypothyroidism is eight times more likely to occur in women than men, and it frequently presents in the later years; older women are the most likely candidates to present with myxedema. The clinical picture of myxedema coma is that of exaggerated hypothyroidism, with dangerous hypoventilation, hypothermia, hypotension, and shock. Coma and seizures can occur as well. Myxedema coma usually develops slowly, has a greater than 50% mortality rate, and requires prompt and aggressive treatment.
Assessment
Signs and symptoms can progress from mild early in onset to life threatening.
Signs and symptoms:
Early fatigue, weight gain from fluid retention, anorexia, lethargy, cold intolerance, hoarseness, ataxia, memory and mental impairment, decreased concentration, menstrual irregularities or heavy menses, infertility, constipation, depression, and muscle cramps. Signs and symptoms may be life threatening in a patient with history of hypothyroidism who has experienced a recent stressful event.
Physical assessment:
Possible presence of goiter, bradycardia, hypothermia, deepened voice, hyperlipidemia, and obesity. Skin may appear yellow and dry, cool, and coarse, and hair may be thin, coarse, and brittle. The tongue may be enlarged (macroglossia), and reflexes may be slowed.
Myxedema coma:
Hypoventilation, hypoglycemia, hypothermia, hypotension, hyponatremia, bradycardia, and shock.
History/risk factors:
Primary hypothyroidism:
Dietary iodine deficiency, thyroid gland radioablation for hyperthyroidism management, thyroid atrophy or fibrosis of unknown cause, radiation therapy to the neck, surgical removal of all or part of the gland, drugs that suppress thyroid activity including propylthiouracil and iodides, invasion of the thyroid gland by tumor (e.g., lymphoma), drugs including lithium and interferon, or a genetic dysfunction resulting in inability to produce and secrete thyroid hormone.
Diagnostic tests
THS
Most commonly used test to detect thyroid dysfunction. It will be elevated unless the disease is long-standing or severe.
131I scan and uptake:
Will be less than 10% in a 24-hr period. In secondary hypothyroidism, uptake increases with administration of exogenous TSH.
Doppler ultrasonography:
To diagnose gland size and abnormal densities, which may be present if nodules are present.
Thyroid autoantibodies:
Presence of thyroperoxidase autoantibodies or antithyroglobulin autoantibodies signals chronic autoimmune thyroiditis.
Thyroid binding globulin:
Measures the level of the protein that binds with circulating thyroid hormones. Abnormal T4 or T3 measurements often occur because of binding protein abnormalities rather than abnormal thyroid function.
Thyroid scan 131I and radioactive iodine uptake:
Identifies thyroid nodules. In primary hypothyroidism, uptake will be less than 10% in a 24-hr period. In secondary hypothyroidism, uptake increases with administration of exogenous TSH.
Nursing diagnosis:
Ineffective breathing pattern (or risk for same)
related to upper airway obstruction occurring with enlarged thyroid gland and/or decreased ventilatory drive caused by greatly decreased metabolism
Desired Outcomes: Patient has an effective breathing pattern as evidenced by respiratory rate (RR) 12-20 breaths/min with normal depth and pattern (eupnea), normal skin color, O2 saturation 95% or more, and absence of adventitious breath sounds. Alternatively, if ineffective breathing pattern occurs, it is detected, reported, and treated promptly.
| ASSESSMENT/INTERVENTIONS | RATIONALES |
|---|---|
| Assess rate, depth, and quality of breath sounds, and be alert to presence of adventitious sounds or decreasing or crowing sounds. | This enables nurse to be alert to presence of adventitious sounds (e.g., from developing pleural effusion) or decreasing or crowing sounds (e.g., from swollen tongue or glottis). |
| Assess for signs of inadequate ventilation. Immediately report significant findings to health care provider. | Decreased respiratory rate, shallow breathing, and circumoral or peripheral cyanosis are signs of inadequate ventilation. Ventilatory insufficiency in a patient with hypothyroid condition can indicate onset of heart failure secondary to impending myxedema coma or hypothyroid crisis. |
| Assess for hypoxemia by measuring O2 saturation intermittently or continuously in patients with increased work of breathing or decreased respiratory rate or depth. | Decreasing O2 saturation (92% or less) may signal need for oxygen supplementation in symptomatic patients. |
| Teach patient coughing, deep breathing, and use of incentive spirometer. Suction upper airway prn. | These measures help clear secretions that may increase with hypoventilation. |
| For patient experiencing respiratory distress, be prepared to assist health care provider with intubation or tracheostomy and maintenance of mechanical ventilatory assistance or to transfer patient to intensive care unit (ICU). | Patient likely will need emergency treatment and intensive care. |
Nursing diagnosis:
Excess fluid volume
related to compromised regulatory mechanisms occurring with adrenal insufficiency
Desired Outcome: By a minimum of 24 hr before hospital discharge, patient is normovolemic as evidenced by urinary output 30 mL/hr or more, stable weight, nondistended jugular veins, presence of eupnea, and peripheral pulse amplitude 2+ or more on a 0-4+ scale.
| ASSESSMENT/INTERVENTIONS | RATIONALES |
|---|---|
| Assess intake and output hourly for evidence of decreasing output. | Decreasing output signals fluid retention leading to hypervolemia. |
| Assess for weight gain by weighing patient at same time every day, with same clothing, and using same scale. Report increasing weight gain to health care provider. | Increasing weight signals fluid retention, which can lead to hypervolemia/volume overload. Weighing patient at the same time and under the same conditions avoids discrepancies that could reflect inaccurate losses or gains. |
| Assess for indicators of heart failure. Report significant findings to health care provider. | Indicators of heart failure include jugular vein distention, crackles, shortness of breath, dependent edema of extremities, and decreased amplitude of peripheral pulses. Lack of thyroid hormones can decrease the heart rate and force of contractions, leading to heart failure. Associated fluid retention worsens the problem. |
| Restrict fluid and sodium intake as prescribed. | This helps prevent fluid retention that could lead to volume overload. |
| Use a rate control device to administer intravenous (IV) fluids. | This will prevent accidental fluid overload. |
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