Hypothyroidism in the Newborn
Edna H. Sobel MD1
Paul Saenger MD1
1 Professor of Pediatrics, Division of Pediatric Endocrinology, Department of pediatrics, Albert Einstein college of Medicine/Montefiore Medical Center, Bronx, NY.
The major thyroid disease of the newborn is congenital primary hypothyroidism, which may be due to agenesis, or maldescent of the thyroid, or to an enzymatic deficiency in the synthesis of thyroxine. Secondary hypothyroidism (due to deficiency of TSH) and tertiary hypothyroidism (due to deficiency of TRH) are rare.
Congenital hypothyroidism is an important cause of mental retardation that can be prevented with treatment. The prevalence of congenital hypothyroidism has been fairly consistent worldwide at 1:4500 newborn infants. The relative prevalence of thyroid-related disorders established by the screening programs is summarized in Table 1.
Screening of all newborns in this country has been under way for about 10 years. Screening is based on analysis of heel-stick-obtained blood collected on filter paper, at the age (3 days) when blood drops are collected for screening of other treatable disorders that can be detected during the newborn period (eg, phenylketonuria).
In this article we will consider the etiology of congenital hypothyroidism, the collection of samples, the analyses to be done, the interpretation of results, the additional tests that may be needed, and the treatment of infants in whom hypothyroidism has been identified and confirmed. Neonatal thyrotoxicosis will also be discussed briefly.
Etiology of Congenital Hypothyroidism
The vast majority of cases of congenital hypothyroidism are sporadic.
