Bone density and turnover in young adult patients with growth hormone deficiency after 2-year growth hormone replacement according with gender

GH deficiency (GHD) in adults is accompanied by reduced bone mass that may revert only after 2 yr of GH replacement. However, it is unclear whether the gender may modify bone responsiveness to GH replacement in adults. In this study we have evaluated whether bone mineral density (BMD) and turnover improve after GH replacement according to patients' gender. BMD at lumbar spine (LS) and femoral neck (FN), serum osteocalcin (OC), and urinary cross-linked N-telopeptides of type I collagen (Ntx) were assessed in 64 hypopituitaric patients (35 men, 30-50 yr) before and 2 yr after the beginning of GH replacement. Values of IGF-I and BMD at LS and at FN were expressed as Zscores. At study entry, IGF-I and BMD resulted similar among men and women with GHD. During GH replacement, IGF-I levels increased in both men and women without any difference in the percentage of IGF-I increase between the genders (p=0.47). In women receiving estrogen replacement, however, the percentage of IGF-I increase (p<0.05), and the Z IGF-I score (p<0.001) were significant lower than estrogen untreated women, although IGF-I levels were similar in the 2 groups (p=0.53). The GH dose adjusted for body weight required to restore normal age- and sex- matched IGF-I levels was lower in men than in women (p<0.001), and was higher in women receiving than in those not receiving estrogen replacement (p<0.05). In contrast, hypogonadal men treated with testosterone and eugonadal men received a similar GH dose (p=0.97). Also OC, Ntx levels, lumbar and femoral BMD improved (p<0.001) in all patients. Nevertheless, a greater increase in lumbar BMD increase was observed in men than in women (8.0+/-2.1 vs 2.6+/-0.4%; p<0.05). No significant difference was revealed in bone parameters in women treated or untreated with estrogen replacement and in men treated or not with testosterone replacement for concomitant hypogonadism. At the multiple correlation analysis, gender was a stronger predictor for the required GH dose than the age (p<0.001 and p=0.02, respectively). In conclusion, a 2-yr GH replacement normalizes IGF-I levels, increases bone mass and improves bone turnover both in men and in women with GHD without any difference between the 2 groups, provided that the dose of GH was modulated on the basis of IGF-I levels. Women receiving oral estrogens should receive a GH dose approximately doubled, as compared to men and women not receiving oral estrogens, to achieve similar effects on bone density and turnover. In particular, GH replacement dose, to be successful on bone mass and turnover, depends on gender in hypopituitary patients aged below 50 yr.