The etiologies and incidences of congenital hypothyroidism before and after neonatal TSH screening program implementation: a study in southern Thailand

Background: Congenital hypothyroidism (CH) is one of the common causes of intellectual disability which can be prevented by early detection of an elevated thyroid stimulating hormone (TSH) level in the newborn and by treatment with thyroxine. In Thailand, neonatal TSH screening was implemented nationwide in 2005. The objective of the study was to determine the etiologies and the estimated incidences of CH in southern Thailand before and after the implementation of a neonatal TSH screening program in 2005. Methods: The medical records of pediatric patients who were diagnosed with primary CH at Songklanagarind Hospital during 1995–2013 were retrospectively reviewed. The study was divided into two time periods: study period 1 (SP1) (1995–2004) and study period 2 (SP2) (2005–2013), the time before and after TSH program implementation. Results: The most common form of CH during SP1 was overt permanent CH (66%), mostly caused by athyreosis or ectopic thyroid. In SP2, the most common form of CH was mild permanent CH (39%) (mostly due to dyshormonogenesis), followed by overt CH (32%) and transient CH (29%). The overall annual estimated incidence of CH per 10,000 live births in Songkhla Province was 1.69 (1:5021) in SP1, increasing to 4.77 (1:2238) in SP2; in all 14 provinces in southern Thailand, the estimated incidence was 1.24 (1:8094) in SP1 and 2.33 (1:4274) in SP2. Conclusions: Neonatal TSH screening has a significant impact on the increased detection of the mild form of permanent and transient CH cases, which may be important for the prevention of brain damage from less severe CH although this remains to be documented.