Growth hormone treatment in adults with GH deficiency: Effects on new biochemical markers of bone and collagen turnover

Serum bone Gla protein (BGP) and bone alkaline phosphatase (B-AP), markers of bone formation, carboxyterminal cross-linked telopeptide of type I collagen (ICTP), marker of bone resorption, and aminoterminal propeptide of type III procollagen (PIIINP) levels, index of collagen synthesis, were determined in 8 adults (mean age±SE: 29.6±1.2 yr) with childhood onset GHD before and after 3 and 6 months of recombinant GH treatment (0.5 IU/kg/week). Before treatment, mean BGP (3.8±.5 ng/ml) and B-AP (44.9±6.9 IU/L) were significantly (p<0.001 and p<0.05, respectively) lower than those recorded in normals (5.4±0.1 ng/ml and 61.8+1.9 IU/L, respectively), while serum ICTP and PIIINP levels were similar to those found in controls (ICTP: 4.7±0.8 vs 4.1±0.3 ng/ml; PIIINP: 3.7±0.6 vs 3.2±0.2 ng/ml). BGP and ICTP levels significantly (p<0.005) increased after 3 (28.4±5.3 ng/ml and 17.5±2.8 ng/ml, respectively) and 6 months (25.1±5.0 ng/ml and 15.0±1.9 ng/ml, respectively) of recombinant GH treatment. B-AP levels significantly (p<0.01) increased during the treatment (basal: 44.9±6.9 IU/L, 3rd month: 173.6±40 IU/L, 6th month: 194.4±40 IU/L), while non B-AP levels remained similar to those recorded in basal condition. Serum PIIINP levels significantly (p<0.0001) rose up after 3 (12.5±1.4 ng/ml) and 6 months (10.2±0.8 ng/ml). Serum BGP and ICTP levels were directly (r=0.85, p<0.001; r=0.53, p<0.01) correlated with serum IGF-I levels. In conclusion, our study show that in adulthood GH deficiency seems to exert less relevant negative effects on bone and collagen turnover than those previously observed in childhood. Furthermore, GH treatment is able to reactivate the bone remodeling of adults with GH deficiency, probably through a local mediation of IGF-I. The long term effect of GH on bone mineral content remains to be established, since recombinant GH treatment increases both bone formation and bone resorption.