Date:
Apr 01, 1996

Two articles in the March 28, 1996 issue of the New England Journal of Medicine1 explore the relationship of a temporary low level of thyroid hormone in premature infants in the first week of life and the occurrence of severe cerebral palsy and/or mental retardation.

One article is the report of a research study supported by the National Institutes of Health (NIH), the government’s medical research agency; the other is an editorial review of the research area by international experts.

The articles point out that thyroxin (thyroid hormone) is necessary for brain development and crosses the placenta from mother to fetus. When the infant is born, its own mechanism becomes active for the production and adjustment of necessary levels of thyroxin. However, it takes time for the premature infant to take over this function; the more premature the infant, the lower the level of thyroxin available to it, particularly in the first few weeks after birth. Most infants are finally able to make the adjustment; thus the low level of thyroxin available is usually a temporary phenomenon — but one that occurs at a critical time in brain development.

In the past, several studies have shown that low levels of thyroxin are present in infants who are mentally retarded. The present study shows that the same is true with those who have severe cerebral palsy.

Comment

Temporary low levels of thyroxin in the premature infant can be associated with the occurrence of severe cerebral palsy.

Does this temporary low level of thyroxin cause brain damage? Or are both due to some other factor influencing the occurrence of both? We don’t know. Should all premature infants be tested shortly after birth for thyroxin levels? Probably. Will treating premature infants who have low levels of thyroxin help prevent cerebral palsy? We don’t know, but a clinical trial would tell us.

The present study is important in that it identifies several specific research questions that can and need to be answered. The Research Foundation is working with the NIH to get the answers.

1″The Relation of Transient Hypothroxinemia in Preterm Infants to Neurologic Development at Two Years of Age;” Reuss M.L. et al. “Prematurity-Associated Neurologic and Developemntal Abnormalities and Neonatal Thyroid Function;” Vulsma, T. and Kok, J.H.

© UCP Research & Educational Foundation, April 1996