CTSZ and osteoporosis: There was a strongly-significant increase in cathepsin Z mRNA in the order: non-osteoporotic control group, osteopenia group and osteoporosis group (Fig. 1a) (one-way ANOVA (F(2,85) = 13.4, P < 0.0001; non-osteoporotic control group vs osteopenia, 95% CI = −0.32 to −0.053, P = 0.0067; non-osteoporotic control group vs osteoporosis, 95%CI = −0.543 to −0.24, P = < 0.0001; osteopenia vs osteoporosis, 95% CI = −0.325 to −0.084, P = 0.0011, post hoc Bonferroni correction).