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Key Features

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  • Growth retardation, decreased physical activity, weight gain, constipation, dry skin, cold intolerance, and delayed puberty

  • Untreated congenital hypothyroidism: thick tongue, large fontanels, poor muscle tone, hoarseness, umbilical hernia, jaundice, and severe neurocognitive impairment

  • T4, FT4, and T3 resin uptake are low

  • Thyroid-stimulating hormone (TSH) levels are elevated in primary hypothyroidism

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Clinical Findings

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  • Even when the thyroid gland is completely absent, most newborns with congenital hypothyroidism appear normal

  • However, because congenital hypothyroidism is associated with intellectual impairment, thyroid testing is included in the newborn screen and treatment must be initiated as early as possible

  • Jaundice associated with an unconjugated hyperbilirubinemia may be present in newborns with congenital hypothyroidism

  • Features of juvenile hypothyroidism include

    • Short stature, abnormal weight gain

    • Delayed bone age and retarded dental eruption

    • Skin changes (dry, thick, scaly, coarse, pale, cool, or mottled, or have a yellowish tinge)

    • Hair changes (dry, coarse, or brittle), hair loss, lateral thinning of the eyebrows

    • Musculoskeletal findings (hypotonia and a slow relaxation component of deep tendon reflexes)

    • Physical and mental sluggishness

    • Nonpitting myxedema

    • Constipation

    • Cold temperature intolerance

    • Bradycardia

    • Delayed puberty; occasional pseudopuberty

  • In hypothyroidism resulting from enzymatic defects, ingestion of goitrogens, or chronic lymphocytic thyroiditis, the thyroid gland may be enlarged

  • Thyroid enlargement in children is usually symmetric, and the gland is moderately firm and not nodular

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Diagnosis

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  • In primary hypothyroidism

    • Total T4 and FT4 may be normal or decreased

    • Serum TSH is elevated

    • Circulating autoantibodies to thyroid peroxidase and thyroglobulin may be present

  • In central hypothyroidism

    • TSH is usually inappropriately normal and associated with a low total T4 and FT4

    • Serum prolactin may be elevated, resulting in galactorrhea

    • Other pituitary deficiencies may be present

  • Thyroid imaging, while helpful in establishing the cause of congenital hypothyroidism, does not affect the treatment plan and is not necessary

  • All newborns should be screened for congenital hypothyroidism shortly after birth

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Treatment

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  • Levothyroxine (75–100 μg/m2/d) is the drug of choice for acquired hypothyroidism

  • In neonates with congenital hypothyroidism, the initial dose is 10–15 μg/kg/d

  • Serum total T4 or FT4 concentrations are used to monitor the adequacy of initial therapy

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