Serum bone Gla protein (BGP), marker of osteoblastic function, carboxyterminal cross-linked telopeptide of type I collagen (ICTP), index of bone resorption, and aminoterminal propeptide of type III procollagen, marker of collagen synthesis, were evaluated in children with GH deficiency (GHD), in adults with childhood-onset GHD and in adults with acquired GHD in adultlife. In children with GHD, serum BGP (12.7 +/- 0.5 ng/ml), ICTP (8.5 +/- 0.9 ng/ml) and PIIINP (3.4 +/- 0.4 ng/ml) were significantly lower (p < 0.0001, p < 0.0001 and p < 0.001, respectively) than those observed in a sex and age matched control group (BGP:18.9 +/- 0.9 ng/ml, ICTP: 14.4 +/- 0.6 ng/ml, PIIINP: 6.7 +/- 0.7 ng/ml). In adults with childhood onsed GHD, BGP levels (3.7 +/- 0.4 ng/ml) were significantly lower (p < 0.0001) than those recorded in a sex and age matched control group (5.4 +/- 0.1 ng/ml), while ICTP (4.7 +/- 0.7 ng/ml) and PIIINP (3.7 +/- 0.5 ng/ml) levels were similar to those found in controls (ICTP: 4.1 +/- 0.3 ng/ml; PIIINP: 3.3 +/- 0.2 ng/ml). In adults with acquired GHD, serum BGP (5.3 +/- 0.4 ng/ml), ICTP (3.8 +/- 0.4 ng/ml) and PIIINP (3.6 +/- 0.3 ng/ml) levels were not significantly different from those recorded in controls (BGP: 5.4 +/- 0.1 ng/ml, ICTP: 4.1 +/- 0.3 ng/ml, PIIINP: 3.3 +/- 0.2 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)