The impact of gender, puberty and body mass on reference values for urinary growth hormone (GH) excretion in normally growing non-obese and obese children

OBJECTIVE There is a lack of normal reference data on urinary GH (u-GH) exc retion in children, We have investigated the impact of age, gender, puberta l development and body mass on reference values for u-GH excretion in norma lly growing non-obese and obese children, STUDY DESIGN u-GH levels were evaluated in 1153 healthy normal children (ag ed 5-14) and in 684 obese children (body mass index, BMI:>75th). u-GH level s (ng/8 h) were determined by ELISA as the mean value of three consecutive first morning voidings, RESULTS Reference values (5-95th centile) for u-GH excretion in obese and n on-obese children of both sexes are reported, In normal prepubertal childre n median u-GH levels were relatively stable and superimposable in the two s exes; subsequently, u-GH levels increased, reaching a peak value at 13 year s in both sexes, Significant increments (P<0.0001) in u-GH levels were show n at B2 for females and at G3 for males. A slight decline was evident at 14 years, In obese children, median u-GH concentrations were significantly lo wer than those recorded in normal children of prepubertal age and at all st ages of puberty (except in females at B2), in spite of their comparable nor mal height, u-GH levels significantly increased at puberty also in obese ch ildren, although the pubertal rise was significantly (P<0.001) lower (1.7-f old in both sexes) than that observed in normal children (2.5-fold in boys and 2.3-fold in girls), A multiple regression analysis showed that both chr onological age (beta: 0.20), BMI (beta: -0.11), gender (beta: -0.04) and pu bertal stage (beta: 0.25) contributed significantly to the physiological va riation in U-GH levels (multiple R: 0.44, P<0.00001), CONCLUSIONS This study provides reference values for U-GH in normally growi ng non-obese and obese children, analysing the impact of gender, puberty an d body mass on this parameter. In agreement with previous studies, which de monstrate blunted GH-responses to provocative stimuli and reduced nocturnal GH concentration, obese children have significantly lower u-GH levels than age-matched normal weight children, both before and during puberty.