Newswise — Preterm infants with low thyroid hormone are significantly more likely to experience neurocognitive deficits at 3 months of age, according to data to be presented on Oct. 4, 2008 at the 79th Annual Meeting of the American Thyroid Association (ATA) in Chicago, IL.

Preterm infants are at risk of both transiently reduced thyroid hormone levels and impaired neurocognitive development. Normal thyroid function is essential for healthy brain development and previous studies have suggested that reduced thyroid function may adversely affect child cognitive development.

A team of researchers from the Hospital for Sick Children and Sunnybrook Health Sciences Centre in Toronto, Ontario, Canada, studied 65 preterm infants born between 24 weeks and 35 weeks gestation. Researchers tested infant's thyroid hormone (fT4, T3, and TSH) levels when the infants were 2 weeks old, 4 weeks old, and at 40 weeks postconceptional age. When the infants were 3 months old, researchers tested their neurocognitive ability with the Bayley Scales of Infant Development (BSID), a series of measurements that assess infants' cognitive development, mental development, and motor development. Researchers then compared the results from the BSID with those of 33 healthy infants born full-term.

Researchers found that infants born before 26 weeks gestation had significantly lower thyroid hormone levels than infants born after 26 weeks gestation. Researchers also found that infants born preterm scored significantly below infants born at full term on the BSID. More specifically, low fT4 levels scored lower on the BSID than infants with normal levels of fT4. Persistent ductus arteriosus and sepsis were two medical morbidities that, in conjunction with low fT4, were associated with worse outcome on the BSID.

"These findings demonstrate that preterm infants born before 26 weeks are significantly more likely to have lower thyroid hormone levels and that hormone deficits contribute to neurocognitive deficits in infants 3 months of age," said study investigator Nevena Simic.

About the American Thyroid Association (ATA)The American Thyroid Association (ATA) is the lead organization in promoting thyroid health and understanding thyroid biology. The ATA values scientific inquiry, clinical excellence, public service, education, collaboration, and collegiality.

A non-profit medical society founded in 1923, the ATA fulfills its mission through supporting excellence and innovation in research, clinical care, education, and public health. ATA members are physicians and scientists who work to enhance the understanding of thyroid physiology and pathophysiology, improve the diagnosis and treatment of thyroid diseases, and promote the education of physicians, patients, and the public about thyroid disorders.

Thyroid diseases are among the most common disorders of the endocrine system, affecting almost 13 million Americans alone. The ATA has extensive online information for patients on thyroid disease (in English and Spanish) serving the clinician as a resource for patients and the public who look for reliable information on the internet.

To learn more about the ATA, visit:

Distribution of information regarding research presented at ATA meetings is thought to be of interest to the public, however, this does not imply official endorsement by the ATA.

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79th Annual Meeting of the American Thyroid Association