Further increase in forearm cortical bone mineral content after discontinuation of growth hormone replacement.

Summary OBJECTIVE Growth hormone replacement of adults with childhood onset GH deficiency results In an Increase In bone mineral density (BMD) after 6-12 months of OH replacement. By measuring BMD 12 months after discontinuation of GH replacement we aimed to Investigate whether there is an effect of GH replacement on BMD persisting after GH has been withdrawn. DESIGN BMD was measured 13 ± 1 (mean ± SE, range 11-16) months after discontinuation of OH replacement. PATIENTS Ten adults, age 23·;2 ±1·;4 (range 18·8-32·4) years, with childhood onset isolated GH deficiency (2 idiopathic, 8 irradiation induced) who had previously completed a study of the effect of 12 months of OH replacement on BMD. MEASUREMENTS Forearm cortical bone mineral content (BMC) was measured using single-photon absorptlometry at the proximal site of the distal forearm. Forearm integral BMC at the ultradistal site of the forearm and bone width at both proximal and ultradistal rites of the distal forearm were measured by the same technique. Vertebral trabecular BMD was measured using quantitative computed tomography. RESULTS Forearm cortical BMC was significantly greater than that measured at the time of discontinuation of OH (1·48 ±0·04 vs 1·44 ± 0·05 g/cm). There was no significant change in forearm integral BMC or in vertebral trabecular BMD after discontinuation of OH. There was no significant change in bone width at proximal and ultradistal sites of the distal forearm after discontinuation of GH. CONCLUSION After discontinuation of OH replacement the further increase In forearm cortical bone mineral content without a significant Increase In forearm bone width suggests that the Increase In cortical bone mineral content Is due to a persisting effect of previous GH replacement, and not to further spontaneous attainment of bone mass before peak bone mass lo reached. These findings emphasize the importance of continuing to monitor bone mass after the stimulus to Increase bone turnover has been withdrawn.