Evaluation of the growth response to growth hormone therapy in short children with normal growth hormone secretion

Abstract

Introduction The availability of biosynthetic growth hormone (GH) ensures that children who are deficient can have replacement therapy, but it has also created the opportunity to treat children who are short but do not have a deficiency. The target height of children with short stature who have normal GH secretion, idiopathic short stature (ISS), without treatment, fails to reach their midparental potential. GH therapy for these children has resulted in variable height outcomes. While some children reached or exceeded genetic target height, others did not have a favorable response. Aim The aim of this study was to report the outcome of the children with ISS who had initial height standard deviation score (HtSDS) (Z score) less than −2, with normal stimulated GH levels (>10 μg/l), after treatment with biosynthetic GH for at least 1 year. Patients and methods This retrospective study included 20 children with ISS, with initial HTSDS less than −2, normal stimulated GH levels (>10 μg/l), who were treated with rhGH (0.04 mg/kg/day) for at least 1 year. None had any other systemic or endocrine disorder. All had normal complete blood count, liver, and renal functions. Results Twenty children (15 males and five females) with ISS, aged between 4.3 and 13.8 years (mean=9.88±2.62 years), who had mean peak GH=15.58±6.95 μg, were studied. All received GH treatment (average GH dose was 0.04 mg/kg/day) for a mean duration=2.49±1.61 years. The mean midparental HtSDS (MPHSDS) was −1.23±0.57. Their bone age did not differ significantly compared with their chronological age (the mean difference=−0.13±0.67 years). The mean HSDS before treatment was −2.34±0.41 and after 1 year of GH treatment was −1.83±0.48. This gave a gain of an average of 0.5 SD. At the last visit (after a mean of 2.5 years), the HtSDS −1.57±0.55 SD with a gain of 0.77±0.14 SD versus before treatment. The difference between children HtSDS compared with their MPHSDS was −1.08 SD before treatment that was changed to −0.3 SD at the last visit. The increment in HSDS was positively correlated with the duration of rhGH therapy (r=0.82, P=0.01) and negatively correlated with age at the start of treatment (r=−0.54, P=0.01). Conclusion Growth hormone therapy that benefits short children with normal growth hormone secretion achieves near-normal HSDS and approaches MPHSDS.