The influence of body mass index on growth hormone secretion in normal and short statured children.

Obesity is one of the factors which limits the value of growth hormone (GH) provocation tests in the diagnosis of GH deficiency. We have therefore examined (1) the relationship between urinary GH (uGH), a physiological parameter of GH secretion, and percent ideal body mass index (BMI%), an indirect estimate of body fat, in 528 schoolchildren; and (2) the extent to which peak arginine stimulated (0.5 g/kg i.v.) GH concentrations were influenced by BMI% in 176 short normal (SN) children and 48 girls with Turner syndrome (TS). The mean BMI% (SD) for each group was 102.9 (10.8) in schoolboys, 102.7 (13.4) in schoolgirls, 95.8 (13.9) in SN boys, 98.2 (21.4) in SN girls and 105.9 (18.0) in TS. BMI% correlated inversely with log uGH in school-children (boys r = -0.16, P = 0.01; girls r = -0.25, P < 0.001). However, if each sex was subdivided by pubertal status, the inverse relationship only persisted in pubertal (boys r = -0.18, P = 0.04; girls r = -0.39, P < 0.001) but not prepubertal children (boys r = -0.1, P = 0.3; girls r = -0.11, P = 0.3). BMI% was also inversely related to log peak stimulated GH concentration in SN girls (r = -0.49, P < 0.001) but not SN boys (r = -0.14, P = 0.2) or girls with TS (r = 0.19, P = 0.2). The inverse relationship between normal body fat and physiological GH secretion becomes significant during puberty; in girls it accounts for 15% of the variability in uGH excretion.(ABSTRACT TRUNCATED AT 250 WORDS)