Investigators from the University of Minnesota conducted a study to assess the predictive value of catch-up growth and normalization of the growth hormone system on the long-term growth and cognitive development of internationally adopted children. Participants were recruited from a larger longitudinal study and were included if they were adopted from institutional care in Eastern Europe and had their initial intake appointment within 1 month of arrival to the United States. Children with suspected fetal alcohol spectrum disorder (FASD), based on FASD facial analysis software, were excluded from study. Assessments were conducted at baseline and at 6 and 30 months postarrival. Anthropometric data were collected at all 3 visits. General cognitive development was assessed using the Mullen Scales of Early Learning at the first 2 visits and the Stanford-Binet Intelligence Scales at the third visit. Blood levels of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) were obtained at the first 2 visits. Anthropometric data were converted to z-scores, and changes from baseline in z-scores in study children analyzed. Predictors of IQ scores at 30 months postadoption were assessed with regression analyses, after controlling for potential confounders.
Data were analyzed on 46 children with a mean age of 18.9 months at adoption. At 6 months postarrival, there were statistically significant improvements in mean height, weight, and occipitofrontal circumference (OFC) compared to baseline values. At 30 months postarrival, there was significant improvement in height and weight z-scores, but not OFC. For both height and weight, the children who were smallest at the time of arrival showed the most catch-up growth by 30 months postarrival.
At 30 months postarrival, 91.3% of children were found to have verbal and nonverbal IQ scores in the normal range. Positive predictors of higher verbal IQ scores at 30 months included general cognitive functioning at 6 months (Mullen scores), change in OFC in the first 6 months postarrival, as well as initial height. Children with lower initial IGFBP3 levels had higher verbal IQ scores at 30 months. Positive predictors of nonverbal IQ scores also included general cognitive functioning at 6 months (Mullen scores) and height-for-age at arrival.
No association was found between IGF1 and cognitive functioning at 30 months postarrival. There were no significant differences associated with gender or age at arrival and catch-up growth or development.
The authors conclude that the extent of the early adversity experienced by these children, manifested by both reduced initial height and abnormal growth hormone function, is predictive of the extent of catch-up in both general cognition and growth. They recommend that if normal rate of catch-up in growth and cognition is not seen at the 6-month postadoption mark, referral should be considered to investigate and intervene as necessary.