BACKGROUND Learning disability and short stature are cardinal signs of Down’s syndrome. Insulin-like growth factor I (IGF-I), regulated by growth hormone (GH) from about 6 months of age, may be involved in brain development.

AIMS To study long term effects of GH on linear growth and psychomotor development in young children with Down’s syndrome.

Study design—Fifteen children with Down’s syndrome were treated with GH for three years from the age of 6 to 9 months (mean, 7.4). Linear growth, psychomotor development, skeletal maturation, serum concentrations of IGF-I and its binding proteins (BPs), and cerebrospinal fluid (CSF) concentrations of IGF-II were studied.

RESULTS The mean height of the study group increased from −1.8 to −0.8 SDS (Swedish standard) during treatment, whereas that of a Down’s syndrome control group fell from −1.7 to −2.2 SDS. Growth velocity declined after treatment stopped. Head growth did not accelerate during treatment. No significant difference in mental or gross motor development was found. The low concentrations of serum IGF-I and IGFBP-3 became normal during GH treatment.

CONCLUSIONS GH treatment results in normal growth velocity in Down’s syndrome but does not affect head circumference or mental or gross motor development. Growth velocity declines after treatment stops.