Stable bone density in adolescents with severe growth hormone deficiency after six months off rhGH.

Abstract

Severe growth hormone deficiency causes lean body mass loss in male adolescents and increased fat mass in both sexes. The changes appear after a 6 month GH pause. The aim was to examine bone density and structure changes in adolescents with severe GHD during a 6-month rhGH treatment interruption. In total, 113 adolescents (20 females) paused rhGH treatment for 6 months at near-final height, and they were retested with arginine-GHRH challenge and basal IGF-1. Severe GHD was diagnosed in 19 individuals (5 females, GH peak <16 ng/ml and IGF-1 < -1.9 SDS) and excluded in 94 (15 females). Bone density and structure were measured by pQCT of the forearm and DXA of the total body at cessation of rhGH and 6 months later. In severe adolescent GHD (sGHD) patients, trabecular density (mg/cm³) decreased from 214 to 202 (p < 0.01); changes in the adolescents with normal test results (tGHD) were from 221 to 214 (p < 0.05). Cortical density (mg/cm³) increased from 1077 to 1099 (p < 0.01) in sGHD patients and from 1060 to 1082 in tGHD patients (p < 0.001). The strength strain index (mm³) showed no significant changes in sGHD patients (306 to 307) but changed from 302 to 315 in tGHD patients (p < 0.05). Total bone area (mm²) shifted from 145.1 to 145.2 in sGHD patients and from 153 to 156 in tGHD patients. Total body aBMD (g/cm²) increased in both groups: from 1.10 to 1.12 in sGHD patients and from 1.11 to 1.14 in tGHD patients (p < 0.01). All bone measurements remained within the reference ranges, and there were no differences between sGHD and tGHD patients. During a 6-month pause of rhGH treatment, the bone structure and density of adolescents with sGHD did not show changes implying harm. Routine retesting of adolescents, including 6 months without GH, is unlikely to be detrimental to the bone.