GREATER SECRETION OF GROWTH-HORMONE IN BLACK THAN IN WHITE MEN - POSSIBLE FACTOR IN GREATER BONE-MINERAL DENSITY - A CLINICAL RESEARCH-CENTER STUDY

To determine why blacks have a higher bone mineral density (BMD) and l ower incidence of osteoporosis and fractures than whites, we investiga ted whether the secretion of GH is higher in black than in white men. Measurements of GH were obtained at 20-min intervals over 24 h and ana lyzed by deconvolution. BMD was determined by dual energy x-ray absorp tiometry in 16 normal black and 17 normal white men, aged 20-40 yr. Th e 24-h integrated GH concentration (942 +/- 174 us. 602 +/- 104 mu g/L ; P = 0.0495) and GH secretory burst amplitude (0.499 +/- 0.163 vs. 0. 169 +/- 0.027 mu g/L . min; P = 0.0482) were higher in black than in w hite men. GH burst frequency, half-duration, mass, and half-life were not different in the 2 groups. The serum 17 beta-estradiol level (162 +/- 12 vs. 108 +/- 11 pmol/L; P = 0.0011) was higher, and the serum in sulin-like growth factor-binding protein 3 level (2.2 +/- 0.1 vs. 2.8 +/- 0.1 mu g/mL; P = 0.0001) was lower in black than in white men. BMD values for total body (1.22 +/- 0.02 us. 1.14 +/- 0.02 g/cm(2); P = 0 .0041), forearm (0.69 +/- 0.01 vs. 0.66 +/- 0.01 g/cm(2); P = 0.0211), trochanter(0.91 +/- 0.03 vs. 0.77 +/- 0.03 g/cm(2); P = 0.0003), and femoral neck (1.08 +/- 0.03 os. 0.93 +/- 0.03 g/cm(2); P = 0.0007) wer e higher in black than in white men. Thus, serum 17 beta-estradiol lev el, GH secretion, and BMD values for the total body, forearm, trochant er, and femoral neck are greater in black than in white men. As estrog en is known to increase GH secretion and GH to increase bone mass, inc reases in circulating 17 beta-estradiol may contribute to the higher G H secretion and bone mass in black men.