Growth hormone, insulin growth factor-1, and IGF binding protein-3 axis relationship with bone mineral density among healthy men

The aim of this study was to investigate serum levels of growth hormone (GH), insulin growth factor-I (IGF-I), and insulin growth factor binding protein-3 (IGFBP-3) in 363 healthy caucasian men with and without decreased bone density, who had never experienced fractures. Mean age was 51 +/- 8.7 years. Height and weight were measured and BMI was calculated using the formula weight (kg)/height (m(2)). Bone mineral density (BMD) was assessed: in 4 skeletal sites (lumbar spine [ LS], femoral neck [FN], Ward's triangle [WT], and trochanter [T]) using dual-energy X-ray absorpsiometry (DEXA). After an overnight fasting, blood samples were taken at 8:00 a. m. Serum concentrations of GH, IGF-I, and IGFBP-3 were measured using the immunofunctional (GH) and IRMA (IGF-I and IGFBP-3) methods. The BMD at the 4 skeletal sites is expressed as mean value +/- SD in g/cm(2) and T score. Forty-four men (11%) had bone mineral density (BMD) less than or equal to -2:5 SD (T score). Mean GH, IGF-I, and IGFBP-3 levels were 0.2 +/- 0.1, 186.1 +/- 177.3, and 4990 +/- 1460 ng/mL, respectively. There were no significant differences between men with normal BMD and men with reduced BMD concerning GH, IGF-I, and IGFBP-3 measurements. In normal men (319), mean GH, IGF-I, and IGFBP-3 levels were 0.4 +/- 0.1, 192 +/- 87, and 4960 +/- 1530 ng/mL, respectively. In the subgroup with reduced BMD (44), mean GH, IGF-I and IGFBP-3 levels were 0.2 +/- 0.1, 179 +/- 72 and 5230 +/- 1270 ng/mL, respectively. An age-dependent attenuation of GH, IGF-I, and IGFBP-3 levels was also found. No correlation was revealed between BMD and GH in the 4 skeletal sites tested. On the contrary, a positive correlation was established between BMD and IGF-I levels in 3 skeletal sites (LS, FN, T). The same was true between BMD and IGFBP-3 in 2 skeletal sites (LS, FN). In conclusion, 11% of Greek healthy males had decreased bone density. No fractures were demonstrated in any individuals. No significant differences were found between men with normal and reduced BMD, with regards to serum GH, IGF-I, and IGFBP-3, although these levels decreased with age. No correlation was found between BMD and GH levels in the 4 skeletal sites. A positive correlation was found between BMD and IGF-I levels in 3 skeletal sites and IGFBP-3 in 2 skeletal sites.