Birth weight affects final height in patients treated for growth hormone deficiency

OBJECTIVE Birth weight influences both postnatal growth and the initial res ponse to GH therapy in GH-deficient subjects, but its relationship to final height is uncertain. Therefore, we examined final height results in a grou p of subjects treated for GH deficiency who were born small, appropriate or large for gestational age (GA). DESIGN Retrospective study. PATIENTS 108 GH-treated patients (age at diagnosis 11.1 +/- 2.0 years) affe cted by idiopathic and isolated GH deficiency (peak <8 mu g/l after pharmac ological and/or nocturnal mean GH concentration less than or equal to 3.3 m u g/l) were examined. Twenty-four had a birth weight <3rd centile (2300 g /- 268 - small for GA), 77 between the 3rd and 90th centile (3216 g +/- 317 : appropriate for GA) and 7 above the 90th centile (4193g +/- 143: large fo r GA). MEASUREMENTS All subjects reached final height (growth velocity < 0.5 cm/ye ar in the last year of treatment) after hGH treatment (range 33-96 months) at a dose of 20U/m(2)/week. The 3 groups of subjects started therapy at a s imilar height for chronological and bone age. RESULTS Final height in the s mall for GA group was -1.71 +/- 0.93 standard deviation score (SDS), signif icantly lower than that of both appropriate (-1.14 +/- 0.83 (P <0.01)) and large (-0.70 +/- 0.89 (P <0.01)) for GA groups. Similarly, the small for GA group had a significantly lower height SDS increment from the start of the rapy to adult height (0.54 +/- 0.84) than both the appropriate (0.99 +/- 0. 78 (P <0.05)) and the large (1.49 +/- 0.84 (P <0.01)) for GA groups. The pe rcentage of subjects with final height above target height was significantl y different in the 3 groups: 21% for the small, 38% for the appropriate and 71% for the large for GA groups (P <0.05). In the whole group of patients there was a positive correlation between birth weight and final height (r = 0.38; P <0.0001). CONCLUSIONS The present study showed that our patients, affected by isolate d and idiopathic GH deficiency but with different birth weights, despite st arting treatment with a similar height and bone age delay, had different au xological outcomes. It seems, therefore, that final height is strongly infl uenced by birth weight which penalizes the smaller newborns and assists the larger ones.