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 lower incidence of osteoporosis and fractures than whites, we investigated 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 analyzed by deconvolution. BMD was determined by dual energy x-ray absorptiometry in 16 normal black and 17 normal white men, aged 20-40 yr. The 24-h integrated GH concentration (942 ± 174 vs. 602 ± 104 μg/L; P = 0.0495) and GH secretory burst amplitude (0.499 ± 0.163 vs. 0.169 ± 0.027 μg/L · min; P = 0.0482) were higher in black than in white men. GH burst frequency, half-duration, mass, and half- life were not different in the 2 groups. The serum 17β-estradiol level (162 ± 12 vs. 108 ± 11 pmol/L; P = 0.0011) was higher, and the serum insulin- like growth factor-binding protein 3 level (2.2 ± 0.1 vs. 2.8 ± 0.1 μg/mL; P = 0.0001) was lower in black than in white men. BMD values for total body (1.22 ± 0.02 vs. 1.14 ± 0.02 g/cm²; P = 0.0041), forearm (0.69 ± 0.01 vs. 0.66 ± 0.01 g/cm²; P = 0.0211), trochanter (0.91 ± 0.03 vs. 0.77 ± 0.03 g/cm²; P = 0.0003), and femoral neck (1.08 ± 0.03 vs. 0.93 ± 0.03 g/cm²; P = 0.0007) were higher in black than in white men. Thus, serum 17β- estradiol level, GH secretion, and BMD values for the total body, forearm, trochanter, and femoral neck are greater in black than in white men. As estrogen is known to increase GH secretion and GH to increase bone mass, increases in circulating 17β-estradiol may contribute to the higher GH secretion and bone mass in black men.