Prediction Model for Adult Height of Small for Gestational Age Children at the Start of Growth Hormone Treatment

Abstract

GH treatment is approved for short children born small for gestational age (SGA). The optimal dose is not yet established. Our objective was to develop a model for prediction of height at the onset of puberty and of adult height (AH). Two GH studies were performed in short SGA children. A total of 150 SGA children with height sd scores (SDS) less than -2, age 3 yr or older, no signs of catch-up growth, available height at the onset of puberty, and at least 1 yr of GH treatment before the onset of puberty were studied. In one study, patients were randomly assigned to either 0.033 or 0.067 mg/kg x d; in the other study all received 0.033 mg/kg x d. In 71 children, AH was reached. Height SDS at the onset of puberty and AH SDS were calculated. Determinants positively related to height SDS at the onset of puberty were: height SDS at the start; target height SDS; and GH dose, whereas age at the start and female gender were negatively related. Positively related to AH SDS were: height SDS and chronological age--bone age at the start; target height SDS; and GH dose, whereas serum IGF binding protein (IGFBP)-3 SDS at the start was negatively related. There was a significant interaction between GH dose and IGFBP-3 SDS, indicating a smaller GH dose effect for higher levels of IGFBP-3. The final model explained 57% of the variance in height SDS at the onset of puberty and 41% of AH SDS. The prediction model for height SDS at the onset of puberty and AH SDS of short SGA children treated with GH provides useful information about the expected long-term growth. Because GH dosage is one of the determinants, the model aids in determining the optimal GH dose for each child.