Etiologies of Congenital Hypothyroidism: 15-Year Experience in a Tertiary Care Medical Center in Southern Thailand

Background: Congenital hypothyroidism (CH) is one of the common causes of mental retardation which can be prevented by early detection and treatment with thyroxine supplementation. In Thailand, neonatal TSH screening was implemented nationwide in 2003.

Objectives: To determine the etiologies of CH before and after neonatal TSH screening program implementation.

Method: The medical records of patients aged 0-15 years with the diagnosis of congenital hypothyroidism during 1995-2012 were retrospectively reviewed. Results: During the study period, 416 children were diagnosed as CH: 76 (18.3%) with transient CH, 147 (35.3%) with mild CH, and 193 (46.4%) with severe CH. Thyroid scans performed in 306 patients with permanent CH revealed eutopic thyroid in 121 cases (39.6%), ectopic thyroid in 102 cases (33.3%), athyreosis in 72 cases (23.5%), and hypoplasia of the thyroid in 11 cases (3.6%) Comparison of etiologies and types of CH between before TSH screening implementation (1995-2004) and after the TSH screening implementation (2005-2012) found that transient CH and mild permanent CH were significantly more commonly diagnosed after TSH screening implementation and eutopic thyroid or thyroid dyshormonogenesis was a significantly common etiology of CH diagnosis by thyroid scan (p<0.001). Transient CH was significantly more frequently diagnosed in preterm than term neonates (p<0.001) with significantly lower levels of screened neonatal TSH and confirmed TSH than the mild and severe permanent CH cases (P<0.001).

Conclusions: Neonatal TSH screening increase the number of cases of transient CH and mild form CH detected resulting in early treatment to prevent permanent brain damage in cases with less severe CH.