Changes in insulin sensitivity at the time of puberty have been linked to changes in growth hormone action. We, therefore, decided to explore whether parameters of carbohydrate metabolism predict height or weight velocity in late prepubertal and early pubertal children (n=18, age 10.8±1.9 years, 7F, Tanner stage 1-3). The stable labelled (6-6 d2 glucose) frequently sampled 3 hour intravenous glucose tolerance test (250 mg/kg) with 1 compartment minimal modelling was used to determine insulin sensitivity(SI) and glucose effectiveness (SG). Mean overnight (20 min sampling) growth homone (MGH), growth hormone binding protein (GHBP), insulin-like growth factor-1 (IGF1), and leptin levels were also obtained at baseline. Height and weight velocities were determined over the following 6 months. Stepwise linear regression revealed:

Height velocity=7.9+1.77*MGH-2.57*SG

(R2=0.66, p<0.001; MGH, p<0.001; SG, p=0.012)

and

Log(Weight velocity)=0.348+0.117*leptin

(R2=0.45, p=0.003)

Insulin sensitivity was not found to significantly predict either height or weight velocity. These results suggest that glucose effectiveness may serve as a better marker for peripheral growth hormone action than IGF1 or GHBP in regards to predicting growth rate in late prepubertal and early pubertal adolescents. The positive relationship between leptin and weight velocity likely reflects increased rate of weight gain in those children who were most overweight at baseline. Clearly, increased leptin levels in obese individuals do not slow future weight gain.