Thyroid peroxidase antibodies in dried blood specimens of newborns.

Previous studies have disclosed that a substantial percentage of infants from mothers with thyroid autoimmunity have antibodies to thyroid peroxidase (TPOAb) at birth. Furthermore, these antibodies have been shown to be of maternal origin. In view of this we thought it would be of interest to determine the prevalence of TPOAb in newborns from an unselected population of women. This was done by retrieving stored dried blood specimens from 240 full-term healthy infants, which had been obtained during 1999 for routine newborn screening. Ten percent of the randomly selected specimens tested TPOAb positive. Thyroid function in the mothers could not be evaluated because all specimens had been tested anonymously. In summary, our results indicate that a significant percentage of newborns were TPOAb positive. It is unclear at this time whether such antibodies reflected maternal thyroid autoimmunity and/or other autoimmune disorders. However, the close association between autoimmune thyroid disease and TPOAb positivity raises the possibility of abnormal thyroid function in some of the mothers.