Prediction model for adult height of small for gestational age children at the start of growth hormone treatment

Context: GH treatment is approved for short children born small for gestational age (SGA). The optimal dose is not yet established.

Objective: Our objective was to develop a model for prediction of height at the onset of puberty and of adult height (AH).

Design and Setting: Two GH studies were performed in short SGA children.

Patients/intervention: 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.d; in the other study all received 0.033 mg/kg-d. In 71 children, AH was reached.

Main Outcome Measures: Height SDS at the onset of puberty and AH SDS were calculated.

Results: 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.

Conclusions: 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.