Initial congenital hypothyroidism severity predicts later cortical abnormalities

By Eleanor McDermid, Senior medwireNews Reporter

Research suggests that the persistent cognitive defects seen in children with congenital hypothyroidism, despite optimal care, are associated with altered cortical thickness.

And these cortical changes are associated with the severity of hypothyroidism at diagnosis, Joanne Rovet (Hospital for Sick Children, Toronto, Ontario, Canada) reported at the European Society of Paediatric Endocrinology annual meeting in Dublin, Ireland.

She suggested that children born with hypothyroidism have “regional areas where neuronal migration isn’t optimally established.”

This then impairs cognitive development, said Rovet, who showed data demonstrating abnormal visuospatial, language, sensorimotor, attention and memory skills in children with congenital hypothyroidism compared with healthy controls. This occurs despite treatment from birth, and the degree of impairment is associated with the severity of hypothyroidism at diagnosis.

The 42 patients in the study, who were an average of 9.2 years old, had been identified by screening at birth and had received adequate T4 treatment from within 2 weeks of birth.

But compared with 42 age- and gender-matched healthy controls, they had cortical thinning in 11 regions and thickening in seven regions. Thinning occurred in four left and seven right regions, mainly in frontal areas and the poles. Thickening, in four left and three right areas, tended to affect posterior regions.

The changes were associated with T4 levels at diagnosis; four regions on the left and three on the right were thinner when T4 levels were lower, while two regions on the left and two on the right were thicker if T4 was lower. For example, the left calcarine sulcus, which is important for visual processing, was thicker in children with lower T4 levels at diagnosis.

Likewise, high levels of thyroid stimulating hormone (TSH) at diagnosis were associated with thinning in two cortical areas – the right middle frontal sulcus and parieto-occipital sulcus. And there were 16 regions – nine in the left hemisphere and seven in the right – that were thicker if TSH was higher.

Cortical thickening in seven regions was significantly associated with a lower IQ, most particularly for the left rectus gyrus and superior frontal gyrus and for two areas in the right orbital gyrus.

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