Clinical tests as predictors of growth response in GH treatment of short normal children

Growth hormone secretion and effects of growth hormone therapy on growth velocity and weight gain in children with Prader-Willi syndrome

Obesity, short stature, decreased growth rate and delayed skeletal maturation are common features of children with Prader-Willi syndrome (PWS). In contrast to PWS, children with simple exogenous obesity have normal or increased growth rate and normal or advanced skeletal maturation. Decreased growth hormone (GH) secretion evaluated by pharmacological or physiological testing associated with increased plasma insulin-like growth factor (IGF-I) and GH-binding protein (GH-BP) levels are also characteristic of simple obesity. In order to understand whether the suboptimal GH secretion in PWS is an artifact of the obesity, we studied 33 obese and 11 non-obese PWS children, aged 2-16 years.GH secretion was evaluated with three pharmacological stimuli (insulin, clonidine and L-dopa) and by spontaneous 24-hour GH secretion. Skeletal maturation was delayed in 70% whereas plasma IGF-I and GH-BP were either low or normal. Forty subjects, including ten non-obese children, had GH deficiency by standard testing (failure to respond to two pharmacological stimuli), and all but one had blunted spontaneous 24-h GH secretion. No significant correlation between body mass index (wt/ht2) and spontaneous 24-h GH secretion (r = 0.145), p > 0.06) or GH-BP levels (r = 0.19, p > 0.07) was found. Thirty documented GH deficient children have completed at least two years of GH therapy. With treatment the overall mean height SD and weight SD changed from -2.2 to -0.8 and from 3.5 to 2.4 respectively (p < 0.0001). No patient has developed diabetes mellitus. In conclusion, growth velocity, skeletal maturation, GH secretion and GH dependent proteins in PWS resemble GH deficiency more than simple obesity. Our ongoing study suggests that GH deficiency in PWS is not an artifact of obesity. Although it is unlikely that GH deficiency is the only cause of decreased growth velocity and increased adiposity in PWS, it is a common feature and significant contributory factor. Long term observation will be required until achievement of adult height to determine whether GH therapy actually improves final height.

Clinical diagnoses of children with extremely short stature and their response to growth hormone

This study was undertaken to determine the prevalence of clinical diagnoses in a group of children with extremely short stature (standard deviation score for height, < -2.5) and to determine whether the classification might help in predicting response to human growth hormone (hGH) treatment. We classified 49 children referred consecutively to our outpatient clinic for evaluation of short stature with heights < -2.5 standard deviation score and bone ages < 9 years for girls or < 10 years for boys (to avoid an effect of puberty on the response to hGH). The diagnostic categories were growth hormone (GH) deficiency, constitutional delay, familial short stature, and primordial short stature. After referral, Turner syndrome was diagnosed in two children. The remaining 47 children were classified according to primary criteria, considered essential for the diagnosis, and secondary criteria, considered necessary but of lesser importance. There were five children, four children, no children, and one child classified, respectively, with GH deficiency, constitutional delay, familial short stature, and primordial short stature by using the most rigorous definitions of the diagnoses. There was significant overlap in the diagnoses other than GH deficiency. Growth hormone deficiency defined by the primary criterion of peak stimulated GH values < 5 micrograms/L was the most definitive. Of the 47 children, 7 were classified as GH deficient by this criterion and 5 were classified as GH deficient by the primary and secondary criteria. The mean pretreatment growth rate (3.1 +/- 1.9 cm/yr) of the group with stimulated GH values < 5 micrograms/L was significantly less than that in the other groups (4.2 +/- 1.5 cm/yr). The mean growth rate of the children with GH deficiency during treatment with hGH was greater than that in the other groups and was 3.4 times greater than the pretreatment growth rate. The mean growth rate of children in the other groups during hGH treatment was twofold greater than the pretreatment growth rate. We conclude that except for GH deficiency, children with an extreme degree of short stature are not easily classified by standard diagnostic criteria, and that most short children have a positive response to hGH therapy regardless of the diagnosis; therefore a specific clinical diagnosis should not be used to exclude children from hGH therapy.