Topic Overview

Severe hypothyroidism in infancy results in slow growth, significant intellectual disability, and developmental delays. Symptoms are seldom apparent at birth. The age at which they appear and their severity depends on how well the infant's thyroid gland works.

Symptoms in infants

• In the first few months of life, symptoms include poor appetite and choking while nursing, failure to gain weight and length, constipation, jaundice, trouble breathing, a hoarse cry, and sluggishness. The baby's belly may be enlarged. His or her skin may feel cold and look mottled, and the genitals, hands, and feet may be swollen.
• Later signs include dry, scaly skin, poor growth of hair and nails, and a delay in the appearance of teeth. The child's growth may be stunted. His or her fingers and toes may be shorter than those of a healthy child. The child's head may look puffy and large, and the tongue may look swollen.

Infants are treated with synthetic thyroid hormone replacement. An infant treated for hypothyroidism within the first month of life grows and develops normally. Treatment must be continued for life. If hypothyroidism occurs after age 3, intellectual disability usually does not occur. But untreated childhood hypothyroidism usually delays a child's physical growth and sexual development.

Symptoms in children and teens

• Early signs may include lethargy and goiter. Other symptoms such as behavior changes, changes in school performance, and persistent belly pain may also be present. These signs are more suspicious in a child whose parents or siblings also have thyroid problems.
• There usually is some delay in growth and development. But it is not as severe as delays that may result from hypothyroidism during infancy. Physical growth and sexual development are mainly affected. The onset of puberty is delayed, and children with hypothyroidism usually look much younger than they are. Children may also gain weight and yet have a slowed growth rate.

Children and teens also need lifelong treatment with synthetic thyroid hormone replacement. With adequate treatment, a child will catch up in height and weight to healthy children of the same age.