The influence of age, size, pubertal status and renal factors on urinary growth hormone excretion in normal children and adolescents.

Overnight urinary growth hormone (GH) excretion was measured in 528 schoolchildren (aged 4-16 years) whose heights and weights were between the third and 97th centiles. Urinary GH increased significantly with age, reaching a maximum in boys at 15-years-old and in girls at 13-years-old. Peak levels were five and three times higher in boys and girls respectively than in 4-year-olds. Maximum urinary GH excretion was seen at breast stages 3 and 4 in girls and at genital stage 4 in boys followed by a decline in both sexes at stage 5. Boys excreted more GH than girls during prepubertal and pubertal years. During prepubertal years there were fluctuations of urinary excretion of GH with age. Height, weight and pubertal status predicted 31% of the variability of urinary excretion of GH, and urinary excretion of creatinine, albumin and N-acetylglucosaminidase (NAG) predicted 52% of the variability. The importance of establishing sound age and sex-related reference ranges for urinary growth hormone is stressed before application of this test to children with growth disorders.