CTSZ and type 2 diabetes mellitus: At baseline, Dickkopf-related protein 1 (DKK1), cathepsin A, cathepsin S, and cathepsin Z were increased in T2D versus controls (p < 0.05), whilst fibroblast growth factor 23 (FGF23) was lower in T2D versus controls (p ≤ 0.05).