Short-term changes in growth and urinary growth hormone, insulin-like growth factor-I and markers of bone turnover excretion in healthy prepubertal children

Childhood growth is a non-linear process. To assess whether there is a bioc hemical correlate of non-linear growth, we have measured free pyridinoline (fPYR) and deoxypyridinoline (fDPYR) excretion in seven healthy prepubertal children, aged 6.1-7.7 years. To examine the link between short-term growt h and hormone output, urinary growth hormone (uGH) and insulin-like growth factor-1 (uIGF-1) were also measured. Height and weight were measured and a timed overnight urine was collected three times per week from September to July, with results expressed as a weekly change in height (Delta height(w) ) or weight (Delta weight(w)), and as weekly average hormone or bone marker excretion (uGH(w), uIGF-1(w), fPYR(w), fDPYR(w)). Subject specific SD scor es (SDS) were derived for each variable. Delta height(w) and Delta weight(w) did not correlate to uGH(w), uIGF-1(w), fPYR(w) or fDPYR(w). Delta height(w) SDS was weakly but significantly corr elated to fPYRy(w)SDS (r = +0.16; P<0.05) and fDPYR(w)SDS (r= +0.15; P<0.05 ). The percentage of high frequency (2-4 weeks) variation in uGHw excretion , as defined by time series analysis, was correlated with the mean uIGF-1(w ) (r= +0.81; P<0.05), which in turn was significantly reduced (92 +/- 38 vs 120 +/- 47 ng; P<0.001) during periods of slow growth (Delta height(w) < 0 .05 cm/week). We conclude that in normal children the amount of urinary fPYR, fDPYR, GH a nd IGF-1 does not provide a direct biochemical correlate of growth from wee k to week. However good growth is associated with a relative increase in fP YR and fDPYR excretion, while poor growth is associated with reduced IGF-1 excretion, which in turn is influenced by the temporal secretory pattern of GH over 2-4 weeks. (C) 2000 Harcourt Publishers Ltd.