• Deladoëy J, Ruel J, Giguère Y, Van Vliet G. Is the incidence of congenital hypothyroidism really increasing? A 20-year retrospective population-based study in Québec. J Clin Endocrinol Metab 2011; 96: 2422–2429.
  1. Highlighted by an editorial (J Clin Endocrinol Metab 2011; 96: 2395–2397).
  2. Induced a change in screening protocol in Quebec (higher threshold for 2nd test – January 2012).
  3. Cited in the Yearbook of Pediatric Endocrinology 2012 (Karger).

Estimating the incidence of CH is influenced by minimal changes in thyrotropin screening cutoffs. The additional cases identified with lower cutoffs have predominantly functional disorders whose impact on intellectual disability, if left untreated, remains to be determined.

The next question is whether these cases of mild CH require L-T4 treatment to attain their full intellectual potential. The original purpose of screening for CH was to identify severe cases in which a benefit was clear (i.e., prevention of intellectual disability). Over the last two decades, this original paradigm progressively shifted to the detection and treatment of all CH cases, including isolated hyperthyrotropinemias. With lowering TSH cutoffs, additional cases are detected and treated but without evidence of benefit of this intervention on intellectual outcome. This lack of obvious benefit might be the reason why, in the United States, more than a third of children labeled as having CH on the basis of neonatal screening no longer receive treatment after age 4 years. If we are to treat patients and not numbers, there is an urgent need to come back to the original intent of screening for CH and, consequently, to evaluate whether newborns with mildly elevated TSH benefit from early diagnosis and treatment.