Objective: We sought evidence of association of candidate single nucleotide polymorphisms (SNP) within the growth hormone-insulin-like growth factor 1 (IGF1) axis, largely selected on the basis of functional data available at the time of our study, with adult bone mass.
Methods: Four hundred ninety-eight men and 468 women aged 59-71 years were recruited. A lifestyle questionnaire was administered, and bone mineral content (BMC) and bone mineral density (BMD) were measured at the lumbar spine and femoral neck. Two hundred fifty-four men and 271 women had repeat bone densitometry 4 years later. DNA was obtained from whole blood samples using standard extraction techniques. Single nucleotide variants in the growth hormone releasing hormone gene (GHRH, G/A 223 Phe75Leu, rs4988492), growth hormone releasing hormone receptor gene (GHRHR, G/A 217, Ala57Thr, rs4988496), the growth hormone secretagogue receptor gene (GHSR, T/C, Gly57Gly, rs495225), and the growth hormone receptor gene (GHR, T/G, noncoding, rs2940944) were analyzed.
Results: In both sexes, allelic variation in the gene encoding GHRH was associated with BMC and BMD at the proximal femur and lumbar spine, with results generally stronger in women. In women, the mean BMC lumbar spine within the GHRH 11 genotype was 56.9 g, while that of the GHRH 12 genotype was 68.4 g [p < 0.001, fully adjusted for age, body mass index, cigarette and alcohol consumption, dietary calcium intake, physical activity, years since menopause, and hormone replacement therapy (HRT) use]; corresponding figures for BMD lumbar spine (GHRH 11 genotype) were 0.96 g/cm(2) versus 1.10 g/cm(2) (p < 0.001 fully adjusted).
Conclusion: We have demonstrated a relationship between allelic variation in the gene encoding GHRH and bone density; we welcome attempts at replication in other populations.