a–c Comparison of serum levels of isomeric aminobutyric acids, D-BAIBA (a), GABA (b), and L-AABA (c), in women with (CASE) or without osteoporotic fractures (Control) at different age. Mean ± SD, n = 13 pairs in the age of 48–59 years group, and n = 14 pairs in the age of 60–80 years group. d, e Correlations between serum D-BAIBA levels and T-score (THIP) from women (48–80 years old), in the group of no osteoporotic fractures (d) and osteoporotic fractures (e). n = 27 for each group. f–h Serum levels of aminobutyric acid isomers, f D-BAIBA, g GABA, and h L-AABA, in women with different number of osteoporotic fracture locations. Mean ± SD, n = 27 for 0 fracture locations, n = 8 for 1 fracture location, n = 10 for 2 fracture locations, and n = 9 for 3–4 fracture locations. i Comparison of serum levels of isomeric aminobutyric acids in patients with appendicular fractures vs. axial fractures. Mean ± SD, n = 9 for axial fractures, and n = 18 for appendicular fractures.