Effects of 42 months of GH treatment on bone mineral density and bone turnover in GH-deficient adults.

OBJECTIVE

To study the effects of GH treatment for up to 42 months on bone mineral density (BMD) and bone turnover.

DESIGN AND METHODS

BMD with dual energy X-ray absorptiometry, serum type I procollagen carboxy-terminal propeptide (PICP), serum type I collagen carboxy-terminal telopeptide (ICTP) and serum IGF-I were assessed in 71 adults with GH deficiency. There were 44 men and 27 women, aged 20 to 59 (median 43) years. Thirty-two patients completed 36 months and 20 patients 42 months of treatment.

RESULTS

The BMD increased for up to 30-36 months and plateaued thereafter. In the whole study group, the maximum increase of BMD was 5.0% in the lumbar spine (P<0. 001), 5.9% (P<0.01) in the femoral neck, 4.9% (NS, P>0.05) in the Ward's triangle and 8.2% (P<0.001) in the trochanter area. The serum concentrations of PICP (202.6+/-11.5 vs 116.3+/-5.4 microg/l; mean+/-s.e.m.) and ICTP (10.5+/-0.6 vs 4.4+/-0.3 microg/l) doubled (P<0.001) during the first 6 months of GH treatment but returned to baseline by the end of the study (130.0+/-10.4 and 5.6+/-0.7 microg/l respectively), despite constantly elevated serum IGF-I levels (39. 6+/-4.1 nmol/l at 42 months vs 11.9+/-0.9 nmol/l at baseline; P<0.001). The responses to GH treatment of serum IGF-I, PICP, ICTP (P<0.001 for all; ANOVA) and of the BMD in the lumbar spine (P<0.05), in the femoral neck and the trochanter (P<0.001 for both) were more marked in men than in women. At the end of the study the BMD had increased at the four measurement sites by 5.7-10.6% (P<0.01-0.001) in patients with at least osteopenia at baseline and by 0.1-5.3% (NS P<0.05) in those with normal bone status (P<0.001 for differences between groups; ANOVA). Among patients who completed 36-42 months of treatment, the number of those with at least osteopenia was reduced to more than a half. The response of BMD to GH treatment was more marked in young than in old patients at three measurement sites (P<0. 05-<0.001; ANOVA). In the multiple regression analysis the gender and the pretreatment bone mass appeared to be independent predictors of three measurement sites, whereas the age independently determined only the vertebral BMD.

CONCLUSIONS

GH treatment in GH-deficient adults increased BMD for up to 30-36 months, with a plateau thereafter. Concurrently with the plateau in BMD the bone turnover rate normalized. From the skeletal point of view GH-deficient patients exhibiting osteopenia or osteoporosis should be considered as candidates for GH supplementation of at least 3-4 years.