title: Multiple factors influencing the incidence of congenital hypothyroidism detected by neonatal screening.
abstract: OBJECTIVE
  Over the years a rise in the incidence of congenital hypothyroidism (CH) has been described worldwide. The aim of our study was to investigate trends in the incidence of CH in Italy over the period 1987-2008, and to investigate which factors may have influenced the CH incidence in our country.
  
  
  METHODS
  Data were derived from the Italian National Registry of Infants with Congenital Hypothyroidism. Since 1998 the laboratory procedures related to neonatal screening for CH have changed drastically. Accordingly, we estimated the CH incidence during the period 1987-1998 (period 1) and the period 1999-2008 (period 2).
  
  
  RESULTS
  The incidence of CH confirmed at birth (including transient hypothyroidism) has increased from 1:3,000 liveborn infants in period 1 to 1:1,940 in period 2 (+54%), whereas the incidence of purely permanent CH increased from 1:3,200 to 1:2,320 (+38%). Lowering of the TSH cutoff was the most important factor contributing to the increase of CH incidence in Italy. Moreover, an increment of 58% of preterm babies with permanent CH was found in period 2 compared with period 1.
  
  
  CONCLUSIONS
  Our results suggest that more than one cause is responsible for the rise in the increasing CH incidence, with lowering of the screening TSH cutoff and an increased survival rate of a growing number of preterm babies both playing an important role.
authors.affiliation: Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Olivieri
authors.forename: Cristina
authors.initials: C
authors.lastname: Fazzini
authors.forename: Emanuela
authors.initials: E
authors.lastname: Medda
mesh_terms: D003409:Congenital Hypothyroidism / Q000401:mortality*; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007234:Infant, Premature; D007558:Italy / Q000453:epidemiology; D008297:Male; D008403:Mass Screening; D012189:Retrospective Studies