MedlinePlus Medical Encyclopedia: Congenital hypothyroidism

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Congenital hypothyroidism

Contents of this page:
Illustrations Alternative names Definition Causes, incidence, and risk factors Symptoms Signs and tests	Treatment Expectations (prognosis) Complications Calling your health care provider Prevention

Illustrations

Thyroid gland

Alternative names Return to top

Cretinism

Definition Return to top

Congenital hypothyroidism describes a newborn with decreased (or, very rarely, absent) thyroid hormone production.

Causes, incidence, and risk factors Return to top

Hypothyroidism in the newborn may result from absence of or abnormal development of the thyroid gland, destruction of the thyroid gland, failure of stimulation of the thyroid by the pituitary, and/or by defective or abnormal synthesis of thyroid hormones.

Incomplete development of the thyroid is the most common defect and occurs at a rate of 1 out of every 3,000 births. Girls are twice as often affected than boys.

Most affected infants have little or no symptoms, because they only have a mild deficiency of thyroid hormone. However, infants that are profoundly hypothyroid often have a distinctive appearance with a puffy-appearing face, a dull look, and a large tongue that protrudes from the mouth, which is usually kept open.

They usually develop this appearance as the disease progresses. They may have dry, brittle hair; low hairline; and jaundice. Feeding is poor and the infant may choke frequently. Constipation is common. Affected children do not cry much, but sleep excessively and are sluggish and inactive. Muscle tone is usually decreased.

If untreated, even mild hypothyroidism can lead to severe mental retardation and growth retardation. Development is delayed early on, often indicated by failure to meet normal milestones.

The appearance of teeth may be delayed. These problems become more severe as the child ages. Growth failure in terms of body length is noted very early.

Symptoms Return to top

floppy infant
thick, protruding tongue
poor feeding
choking episodes
constipation
prolonged jaundice
short stature

Signs and tests Return to top

sutures - separated widely and a large posterior fontanelle
large fontanelle and posterior fontanelle (soft spots)
dull-appearing facial features
dry, brittle hair and low hairline
short, thick neck
growth failure
short extremities
broad hands with short fingers
myxedema
hypotonia
hoarse-sounding cry or voice

Tests include

X-ray of the long bones
free (unbound) T4 (thyroxine) levels
serum TSH level
serum TBG level (if total thyroxine values are measured)
thyroid scan (technetium)

Treatment Return to top

Early diagnosis is imperative. Most of the effects of hypothyroidism are easily reversible. However, critical development of the nervous system takes place in the first few months after birth. Thyroid hormone deficiency may result in irreversible damage to the nervous system with marked mental retardation.

Replacement therapy with thyroxine is the standard approach to treatment of hypothyroidism. Once medication starts, the blood levels of TSH and free T4 are monitored to keep the values within a normal range.

Expectations (prognosis) Return to top

Very early diagnosis generally results in a good outcome for the infant, in terms of growth and mental capability. Newborns diagnosed and treated in the first month to month and a half generally develop normal intelligence. Absence of thyroid hormone during early life gives a poor outlook in terms of mental development.

Complications Return to top

mental retardation
growth retardation

Calling your health care provider Return to top

Call your health care provider if you feel your child shows signs or symptoms of hypothyroidism, if you are pregnant and are exposed to antithyroid drugs or procedures, or have signs and symptoms of hypothyroidism.

Prevention Return to top

Absence of the thyroid and defective thyroxine production are not preventable. Destruction of the thyroid in the fetus may occur if the mother is treated with radioactive iodine for thyroid cancer while she is pregnant. Infants of mothers taking antithyroid medications should be observed carefully after birth for evidence of drug induced transient (brief) hypothyroidism.

Most states mandate a routing screening test on all newborns to detect hypothyroidism.

Update Date: 1/20/2004

Updated by: John Goldenring, M.D., M.P.H., Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network.

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