Intellectual disability caused by a disease known as Congenital Hypothyroidism may be 'over screened' say researchers at the CHU Sainte-Justine Research Center leading numbers of diagnosed patients to rise in recent figures.

"Overly sensitive screening methods that identify mild cases of CH represent an obvious shift from its original purpose" said Dr. Johnny Deladoëy at the Center, "Which was to identify severe cases in which the benefits from treatment would be clearly documented"

Their from data arises from over of testing 20 years at the Centre hospitalier universitaire de Québec where 1,660,857 newborns were screened.

Whilst some hospitals report hypothyroidism cases rising, their data shows no change in the overall velocity of the disease being stable at roughly 600 cases over the last twenty years.

What changed in their figures appears to be the threshold at which doctors are now labelling the disease, with a directly proportional relationship between how many cases were diagnosed and the level of threshold at which they were identified.

The lack of consensus about the thresholds on which to base detection has always presented a challenge for CH screening, writes the University of Montreal who led the study.

CH and its major consequence intellectual disability, occurs in newborns, and can be prevented through hormone replacement during the second week of life provided it has been identified early.

Discussion about what threshold to diagnose patients may now ensue.