Factors Determining Pubertal Growth and Final Height in Growth Hormone Treatment of Idiopathic Growth Hormone Deficiency

A total of 195 children (117 males and 78 females) with idiopathic growth hormone deficiency (IGHD), treated with growth hormone (GH) for at least 1 year before puberty onset and who had completed treatment to adult height, were selected from the KIGS database for study of growth during puberty. Spontaneous and induced puberty started at 13.8 and 14.9 years in boys and at 12.9 and 13.7 years in girls, respectively. Duration of GH treatment and height gained prepubertally were greater when puberty was induced; prepubertal catch up growth (expressed as a percentage of the difference between target height and height at start of GH) was greater when puberty was induced in boys (59% induced vs. 45% spontaneous, p < 0.001), and in girls (72% induced vs. 53.9% spontaneous, p < 0.01). Final height was attained at 17.8 and 19.2 years in boys and at 16.0 and 17.0 years in girls following spontaneous and induced puberty, respectively. Final heights were greater after induced puberty compared with spontaneous puberty in boys (171.3 vs. 166.0 cm, p < 0.001) and in girls (157.0 vs. 155.0 cm, n.s.). Target height was also significantly greater in boys with spontaneous puberty (172.2 cm vs. induced = 174.2 cm) as compared to girls (spontaneous = 158 cm vs. induced = 160 cm). Duration of pubertal growth was longer in boys compared to girls (3.6 vs. 3.0 years, p < 0.001) and was negatively correlated with age, height, and distance from target height at onset of puberty, but was not correlated with the dose of GH. Catch-up growth during puberty (expressed as a percentage of the difference between target height and height at puberty onset) after induced and spontaneous puberty was 87.9% and 80.8% (not significant) in boys and 66.4% and 75.5% (not significant) in girls. Total pubertal growth (TPG) (cm) was inversely correlated with prepubertal growth by simple linear regression. Multiple linear regression analysis indicated 5 independent predictors of TPG accounting for 78% of the variability, namely sex (boys grew more), distance of target height from height at onset of puberty (+), dose of GH at onset of puberty (+), age at onset of puberty (-), and age at end of growth (+).