Urinary insulin-like-growth factor I in normal children: relationship to age, pubertal status and urinary growth hormone.

Authentic insulin-like growth factor 1 (IGF-I) can be detected in human urine at one thousandth of the serum level, with which it correlates closely. The aim of this study was to establish the normal range of urinary IGF-I (uIGF-I) in relation to age, sex, and pubertal status, and to define the relationship between uIGF-I and urinary growth hormone (uGH). IGF-I was measured by RIA after acid extraction of IGF-I binding protein, and separation by gel chromatography in 302 healthy children (149 boys and 153 girls) in whom uGH had already been measured. The mean amount of uIGF-I excreted each night ranged from 17.5 ng (males) and 14.9 ng (females) at pubertal stage I (PS 1), to a peak of 66.8 ng (males) at PS 4, and 55.8 ng (females) at PS 3, coinciding with peak uGH excretion. Highly significant correlations were found between uGH and uIGF-I both before and during puberty (P < 0.01). These findings extend the range of non-invasive investigation available in growth disorders and physiological studies.