Urinary GH and IGF-I excretion in nine year-old children: relation to sex, current size and size at birth.
OBJECTIVE
To study the relationship of 24-hour urinary growth hormone (GH) and IGF-I excretion in childhood to sex and body size. To test the hypothesis that small size at birth followed by postnatal catch-up growth is associated with elevated IGF-I production.


METHODS
Follow-up study of a cohort of 183 healthy children born in Salisbury, UK.


METHODS
Weight and height, 24-h urinary growth hormone (uGH) and IGF-I (uIGF-I) excretion, and systolic and diastolic blood pressures.


RESULTS
At 9 years of age, 24-h uIGF-I excretion, but not uGH excretion, was strongly related to current weight (P < 0.001) and height (P < 0. 001). Urinary GH and IGF-I excretion were positively correlated (r = 0.15, P = 0.05). Boys excreted more uIGF-I per unit uGH than girls (uIGF-I/uGH molar ratio 32.1 compared to 21.0; P for difference = 0. 002). There were no significant relationships of uGH, uIGF-I or uIGF-I/uGH molar ratio with birthweight, birthlength or head circumference at birth, nor with blood pressure at 9 years. 'Catch-up' growth, indicated by an increase in height SD scores between birth and 9 years, was associated with higher IGF-I excretion (P = 0.01) and occurred in children with taller parents (P < 0.001).


CONCLUSIONS
Boys appear to be more sensitive to GH than girls, generating more uIGF-I in relation to uGH. Urinary IGF-I excretion at 9 years is related to both absolute height and to the degree of catch-up in height from birth. Our results suggest that IGF-I production is strongly influenced by genetic factors, but also by either the degree to which intrauterine growth falls short of genetic growth potential, or the process of postnatal catch-up growth that follows.
MRC Environmental Epidemiology Unit, University of Southampton, Southampton General Hospital, UK. chdf@mrc.soton.ac.uk
C H
CH
Fall
P M
PM
Clark
P C
PC
Hindmarsh
P E
PE
Clayton
A W
AW
Shiell
C M
CM
Law
D000886:Anthropometry; D001724:Birth Weight; D001794:Blood Pressure / Q000502:physiology; D001824:Body Constitution / Q000502:physiology*; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006128:Growth / Q000502:physiology; D019382:Human Growth Hormone / Q000652:urine*; D006801:Humans; D007231:Infant, Newborn; D007334:Insulin-Like Growth Factor I / Q000652:urine*; D008297:Male; D012737:Sex Factors
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I