Primary congenital hypothyroidism: clinical characteristics and etiological study.

Forty-eight children with primary congenital hypothyroidism, who attended Chiang Mai University Hospital, during 1977-2000, were reviewed. The female to male ratio was 2:1. The age at diagnosis ranged from 1 month to 12 years 4 months, with 27% of the cases diagnosed within the first three months of life, 37.5% within the first year, and 62.5% after one year of age. Constipation, delayed development and growth, feeding problems, prolonged neonatal jaundice and goiter were more common. Prolonged neonatal jaundice was found in every case diagnosed within the first three months. The other common signs were dry or mottled skin, abdominal distension, macroglossia, short stature, puffy face and umbilical hernia. Kocher-Debré-Semelaigne syndrome comprised 18.7% of cases with a 2:1 female to male ratio, and it was found in various forms of hypothyroidism. Thyroid scintigrams were done in 47 patients. Thyroid dysgenesis was the most common etiology (80.9%), which consisted of 40.4% athyreosis, 4.3% hypoplasia, and 36.2% thyroid ectopy. Thyroid dyshormonogenesis accounted for 18.9%, in which only 4 of 9 presented with goiter. Two-thirds of these patients showed a positive result to the perchlorate discharge test, indicating an organification defect. A 11 patients had elevated serum TSH level greater than 50 mU/L. The serum T4 level below 2 microg/dL was observed in 17 of 19 patients with athyreosis, 11 of 1 7 with thyroid ectopy, and 6 of 9 with thyroid dyshormonogenesis. These findings including retarded bone age were unable to differentiate among different groups of hypothyroidism.