Endocrine Abstracts

Congenital hypothyroidism (CH) is the most frequent endocrine congenital defect affecting about 1:3000 newborns. In economically/ socially advanced counties, CH is routinely screened by means of TSH (and/or T4) measurement on dry blood spot (dbs) since more than 20 years. Neonatal screening allows early recognition and treatment of affected newborns. Upon data collected in years <2000 by the Italian CH Registry, the newborns with confirmed CH and gland-in-situ constituted about 20% of total CH cases. However, in more recent years the technical improvements in TSH determination in the Center for Neonatal Screening of Milan region have lead to a progressive lowering of dbs TSH cutoff value for newborn recall down to 10 mU/l. This has resulted in a significant increase of the recall rate for CH (CH incidence 2003: 80/91,948 newborns), with gland-in-situ cases nowadays accounting for more than 55% of total CH cases. This phenomenon has several important implications concerning the correct diagnosis and adequate management of these babies. One of the most important questions raised by this new picture concerns the necessity to treat babies with mild TSH elevations. The possibility to give correct answers to these questions is complicated by the extreme heterogeneity of this CH category, highlighted by the variable thyroid phenotype as well as by the multiple possibilities of association with non-thyroid malformations/disorders. Relevant advancements have been done in recent years with the discovery of new genetic causes and the description of their underlying molecular mechanisms and related phenotypic presentation. Nevertheless, the cause of several gland-in-situ CH cases remains still unsolved justifying further efforts in this research field. These efforts will contribute to reach a more complete pathogenic classification of CH with gland-in-situ which represents one of the major steps toward an improved and evidence-based clinical management of CH patients.