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 biochemical 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 growth and hormone output, urinary growth hormone (uGH) and insulin-like growth factor-I (ulGF-I) 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 (Δheight(w)) or weight (Δweight(w)), and as weekly average hormone or bone marker excretion (uGH(w), ulGF-I(w), fPYR(w), fDPYR(w)). Subject specific SD scores (SDS) were derived for each variable. Δheight(w) and Δweight(w) did not correlate to uGH(w), ulGF-I(w), fPYR(w) or fDPYR(w), Δheight(w) SDS was weakly but significantly correlated to fPYR(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 uGH(w) excretion, as defined by time series analysis, was correlated with the mean ulGF-I(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 (Δheight(w) < 0.05 cm/week). We conclude that in normal children the amount of urinary fPYR, fDPYR, GH and IGF-I does not provide a direct biochemical correlate of growth from week to week. However good growth is associated with a relative increase in fPYR and fDPYR excretion, while poor growth is associated with reduced IGF-I excretion, which in turn is influenced by the temporal secretory pattern of GH over 2-4 weeks. (C) 2000 Harcourt Publishers Ltd.