Objective: To determine the influence of birth weight on the first year response to growth hormone (GH) replacement in children with isolated GH insufficiency.
Study design: A longitudinal study of response to daily GH treatment (15-26 IU/m2/week) was performed in 16 singleton Caucasian prepubertal children (11 boys, 5 girls) with isolated GH insufficiency (peak GH response to insulin tolerance test <13.5 mU/L) attending a pediatric endocrinology clinic. Change in height velocity standard deviation scores, during the 6 to 12 months before starting GH and the 12 months after, were used to reflect responsivity to GH treatment. Potential influencing variables considered by regression analysis were birth weight standard deviation score (BWSDS), peak GH response to insulin tolerance testing, midparental height standard deviation score, age at treatment, and dose of GH administered.
Results: Mean BWSDS was -0.51 (SD, 1.0). Change in height velocity standard deviation score was correlated positively with BWSDS (r = 0.64) and negatively with peak GH (r = -0.59). Stepwise linear regression analysis confirmed the influence of BWSDS on response to GH treatment.
Conclusions: The continuum of birth weight influences initial responsivity to GH treatment in GH-insufficient children. This may reflect relative insensitivity in the growth hormone or insulin-like growth factor axis. The influence of birth weight on final height and benefit of using higher doses of GH in these children remains to be seen.