Responses of markers of bone and collagen turnover to exercise, growth hormone (GH) administration, and GH withdrawal in trained adult males

To examine the interactions between acute exercise and GH on markers of bon e and collagen turnover and to assess the potential for detecting GH abuse in athletes using these markers, we studied 17 aerobically trained males (a ge, 26.9 +/- 1.5 yr). Sequential studies of exercise, GH administration, an d GH withdrawal were undertaken. A randomized, controlled study of rest vs, exercise showed that exercise did not change serum osteocalcin; other mark ers of formation increased transiently teach P < 0.001): bone-specific alka line phosphatase (+16.1%), carboxyterminal propeptide of type I procollagen (+14.1%), and procollagen III N-terminal extension peptide (+5.0%). The ca rboxyterminal cross-linked telopeptide of type I collagen, a bone resorptio n marker, increased 9.7% (P = 0.018) in response to exercise. A randomized, double blind, placebo-controlled, parallel study of recombinant human GH t reatment (0.15 IU/kg.day) for 1 week increased serum osteocalcin (net incre ase preexercise, + 10.0%; P = 0.017), carboxyterminal propeptide of type I procollagen (+17.6%; P = 0.002), procollagen III N-terminal extension pepti de (+48.4%; P = 0.001), and carboxyterminal cross-linked telopeptide of typ e I collagen (53.3%; P = 0.009). Disappearance half-times after cessation o f recombinant human GH for pre- and postexercise markers ranged from 248 - 770 h. We conclude 1) endurance exercise transiently activates bone and col lagen turnover; 2) brief GH administration results in similar but quantitat ively greater augmentation; and 3) these data will assist in designing a GH detection strategy.