Management and outcome of children with congenital hypothyroidism detected on neonatal screening in South Australia

Abstract

Thirty-eight congenitally hypothyroid children who were detected in a neonatal screening programme have been treated for a mean period of 3.8 years (range, 0.5-8.5 years) by the maintenance of the free thyroxine index in the upper normal range as the main determinant of the dose of thyroxine. Only excessive elevation of, or serial rises in, thyroid stimulating hormone (TSH) level influenced the dose of thyroxine. This treatment strategy, which aims to avoid the potentially adverse effects of thyroxine overdosage, has often resulted in delayed return of TSH levels to normal, especially in athyrotic children (mean TSH +/- SD at one year of age in athyrotic children, 72 +/- 90 mU/L; in children with ectopic thyroid glands, 24 +/- 16 mU/L; normal range, 0-7 mU/L). The mean thyroxine dose of about 100 micrograms/m2 did not change significantly with age, and is lower than the doses that are sometimes quoted in the literature; athyrotic children require significantly more thyroxine (P less than 0.05) than those with ectopic thyroid glands. Symptoms and signs of congenital hypothyroidism, although subtle, were significantly more common (P less than 0.05 for symptoms and P less than 0.001 for signs) in athyrotic children compared with those with ectopic glands. No physical or developmental abnormality related to congenital hypothyroidism has been demonstrated on follow-up; mean height and weight percentiles approximate the 50th percentile at ages one to six years and mean developmental scores +/- SD at about two years of age by the Griffiths Mental Development Scale and at 4.5-6.5 years by the Wechsler Preschool and Primary Scale are 102.4 +/- 10.4 and 111.2 +/- 12.2, respectively. Long-term follow-up studies are necessary to exclude more subtle developmental and neurological abnormalities.