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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Thyroid-stimulating hormone (TSH) levels above normal range (primary hypothyroidism).

  • Low free T4 or low free thyroxin index (FTI)

GENERAL CONSIDERATIONS

  • Hypothyroidism is caused by thyroid hormone insufficiency

  • Myxedema refers to profound hypothyroidism resulting in severe hypothermia, hypoventilation, and hypotension with signs of neurologic impairment

  • Hypothyroidism accelerates atherosclerosis, but angina and myocardial infarction are rare until thyroid hormone is replaced because of the reduced metabolic demands of the hypothyroid state

  • Hypothyroidism can be caused by:

    • – Thyroid disease (eg, Hashimoto’s thyroiditis)

    • – Congenital abnormalities

    • – Iodine deficiency

    • – Drugs such as lithium

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Weight gain, weakness, lethargy, cold intolerance, dry skin, and coarse hair

  • Amenorrhea or impotence

  • Dyspnea on exertion

PHYSICAL EXAM FINDINGS

  • Bradycardia

  • Mild diastolic hypertension

  • Pleural effusions

  • Hypothermia

  • Goiter in some

  • Distant heart sounds

  • Delayed reflexes in the return phase

  • Nonpitting edema (myxedema)

DIFFERENTIAL DIAGNOSIS

  • Congestive heart failure due to other causes

  • Other causes of effusions and edema

  • Hyperlipidemia and atherosclerosis without hypothyroidism

  • Amiodarone toxicity

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • Elevated TSH, reduced T4, T3, and FTI

  • Hyperlipidemia is common

  • Anemia

  • Elevated antithyroid antibodies in Hashimoto’s disease

ELECTROCARDIOGRAPHY

  • Sinus bradycardia

  • Low or flattened T waves

  • Increased PR and QT intervals

IMAGING STUDIES

  • Echocardiography:

    • – Pericardial effusion common, but signs of tamponade unusual

    • – Reduced cardiac performance

DIAGNOSTIC PROCEDURES

  • Coronary angiography may be necessary

TREATMENT

CARDIOLOGY REFERRAL

  • Suspected cardiac disease

HOSPITALIZATION CRITERIA

  • Heart failure symptoms and signs

MEDICATIONS

  • Thyroid hormone replacement, which must be given slowly to older patients or those suspected of having coronary artery disease, to prevent exacerbation of angina and precipitation of myocardial infarction

THERAPEUTIC PROCEDURES

  • Coronary revascularization should be considered before thyroid replacement therapy in high-risk patients

MONITORING

  • ECG monitoring in hospital as appropriate

  • TSH levels during treatment

DIET AND ACTIVITY

  • Low-fat diet

  • Reduced activity until condition improves

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

  • Resolution of problem

FOLLOW-UP

  • As appropriate for condition

COMPLICATIONS

  • Heart failure

  • Angina or myocardial infarction during treatment

PROGNOSIS

  • Excellent in the absence of heart disease

PREVENTION

  • Continue thyroid hormone replacement ...

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