Epidemiology of congenital hypothyroidism

Abstract

Congenital hypothyroidism (CH) is the most common congenital endocrine disorder and one of the most common preventable causes of mental retardation. Over the years, a rise in the incidence has been described worldwide with a rate ranging currently between 1:1,660 and 1:2,828 live births. Epidemiological studies have shown that more than one cause is responsible for the rise in CH incidence worldwide. Both lowering of the screening TSH cutoff and improvements in neonatal medicine, which have increased the survival rate of a growing number of preterm babies, have played an important role. Moreover, the adoption of special screening procedures for at-risk newborns, a changing demography due to migration flows, and environmental factors such as iodine deficiency contribute to explain the large variability of the CH incidence in different countries. In this chapter, the most important issues regarding epidemiology of CH will be reviewed and discussed.