Congenital Hypothyroidism

Congenital hypothyroidism (CH) is a common yet preventable cause of intellectual disability. The prevalence of CH has risen since the advent of newborn screening (NBS), in part due to improvements in screening methodology. Before the introduction of NBS in the 1970s, CH was identified in approximately 1:4000 births. In some parts of North America, prevalence rates have been reported to range from 1:1404 to 1:4149. Thus, CH is more common than once suspected and more important to diagnose appropriately and treat in a timely fashion. Complications of undiagnosed hypothyroidism include growth failure and severe disability in cognitive, emotional, and gross motor function. In underdeveloped countries, severe hypothyroidism continues to be one of the most common causes of cognitive impairment in children. Though nearly eradicated in developed areas with the introduction of iodination of salt and screening in the newborn period, intellectual disability resulting from iodine deficiency and thyroid disease still affects millions of children worldwide. When discovered on NBS, CH care requires caregiver education, consistent therapy, and frequent assessment of laboratory and clinical outcomes. Even within industrialized countries, undiagnosed and untreated CH continues to result in irreversible handicaps. Screening alone is not enough to mitigate the untoward effects of CH. Confirmation of diagnosis, adequate treatment, and clinical follow-up of CH patients in a timely fashion can prevent cognitive impairment and mediate adequate growth and development in most children. This chapter provides practical guidelines for the diagnosis and management of CH.