Fifteen years of GH replacement increases bone mineral density in hypopituitary patients with adult-onset GH deficiency

Objective: Few studies have determined the effects of more than 5-10 years of GH replacement in adults on bone mineral content (BMC) and bone mineral density (BMD). Design/patients: In this prospective, single-centre, open-label study, the effects of 15 years of GH replacement on BMC and BMD, measured using dual-energy X-ray absorptiometry, were determined in 126 hypopituitary adults (72 men) with adult-onset GH deficiency (GHD). Mean age was 49.4 (range 22-74) years at the initiation of the study. Results: The mean initial GH dose of 0.63 (S.E.M. 0.03) mg/day was gradually lowered to 0.41 (0.01) mg/day after 15 years. The mean serum IGF1 SDS increased from -1.69 (0.11) at baseline to 0.63 (0.16) at the study end (P < 0.001 vs baseline). The 15 years of GH replacement induced a sustained increase in total body BMC (+5%, P < 0.001) and BMD (+2%, P < 0.001). Lumbar (L2-L4) spine BMC increased by 9% (P < 0.001) and BMD by 5% (P < 0.001). In femur neck, a peak increase in BMC and BMD of 7 and 3%, respectively, was observed after 7 years (both P < 0.001). After 15 years, femur neck BMC was 5% above the baseline value (P < 0.01), whereas femur neck BMD had returned to the baseline level. In most variables, men had a more marked response to GH replacement than women. Conclusions: Fifteen-year GH replacement in GHD adults induced a sustained increase in total body and lumbar (L2-L4) spine BMC and BMD. In femur neck, BMC and BMD peaked at 7 years and then decreased towards baseline values.