Effect of Body Mass Index on Peak Growth Hormone Response to Provocative Testing in Children with Short Stature

Abstract

Context: Obesity is associated with decreased spontaneous and stimulated GH secretion, but the effect of body mass index (BMI) on results of GH stimulation testing in children with short stature is not known. Objective: The aim of the study was to determine the impact of BMI on peak GH to provocative testing in children with short stature. Design, Setting, and Participants: This was a retrospective review of provocative GH testing performed in 116 children 2–18 yr old in the ambulatory clinic of the Pediatric Endocrinology Unit at the Massachusetts General Hospital from 2004–2008. Main Outcome Measures: The main outcome measure was peak stimulated GH. Height, weight, IGF-I, and IGF-binding protein 3 were also measured. Results: In univariate regression analysis, BMI sd score (BMI SDS) was inversely associated with natural log (ln) peak GH to provocative testing (P = 0.002), whereas height SDS, ln IGF-I, and IGF-binding protein 3 were not significantly associated with ln peak GH. After controlling for age, gender, BMI, and pubertal status, BMI (P = 0.002) remained independently associated with ln peak GH. BMI SDS significantly influenced the likelihood of diagnosis of GH deficiency using peak GH cutoffs of 10, 7, and 5 μg/liter. Conclusion: In children with short stature, BMI affects peak stimulated GH and should be considered when interpreting GH testing. Higher BMI SDS, even within the normal range, may lead to overdiagnosis of GH deficiency.