Notably, irisin, a muscle-produced hormone that was first identified a few years ago [113], was found to be correlated with the bone status in T2DM; namely, irisin was negatively correlated with β-CTX, being lower in osteoporotic subjects with newly detected T2DM versus those with normal DXA results according to one study published in 2022 [114] (Figure 2). This evidence concerns the gene FNDC5 and type 2 diabetes mellitus.