Late effects of early growth hormone treatment in Down syndrome

Down syndrome (DS) is associated with short stature and psychomotor delay. We have previously shown that growth hormone (GH) treatment during infancy and childhood normalizes growth velocity and improves fine motor skill performance in DS. The aim of this study was to investigate late effects of early GH treatment on growth and psychomotor development in the DS subjects from the previous trial.

Twelve of 15 adolescents with DS (3 F) from the GH group and 10 of 15 controls (5 F) participated in this follow-up study. Fifteen other subjects with DS (6 F) were included as controls in anthropometric analyses. Cognitive function was assessed with the Leiter International Performance Scale-Revised (Leiter-R) and selected subtests of the Wechsler Intelligence Scale for Children, Third edition (WISC-III). The Bruininks-Oseretsky Test of Motor Proficiency, Second edition (BOT-2), was used to assess general motor ability.

Although early GH treatment had no effect on final height, the treated subjects had a greater head circumference standard deviation score (SDS) than the controls (-1.6 SDS vs. -2.2 SDS). The adolescents previously treated with GH had scores above those of the controls in all subtests of Leiter-R and WISC-III, but no difference in Brief IQ-score was seen between the groups. The age-adjusted motor performance of all subjects was below -2 SD, but the GH-treated subjects performed better than the controls in all but one subtest.

The combined finding of a greater head circumference SDS and better psychomotor performance indicates that DS subjects may benefit from early GH treatment.