Circulating Irisin as a Possible Marker of Glucose and Bone Metabolism: Evidence from the IRI-OP-OB Pilot Study

Background: Irisin, a recently discovered muscle-originating hormone, has been found to act as a biomarker of several ailments, while no guideline clearly indicates its testing so far in any particular population category or pathological condition. Objective: We analyzed blood (circulating) irisin in relation to the potential correlations with the evaluation of glucose and bone profile. Methods: This was a prospective, pilot, exploratory study (between December 2024 and August 2025). The enrolled patients were menopausal women aged ≥50. Exclusion criteria: Endocrine tumors, thyroid dysfunction, malignancies, or chronic kidney disease. Baseline (fasting) testing was followed by 75 g oral glucose tolerance test (OGTT). Enzyme-linked immunosorbent assay (ELISA)-based irisin assay (MyBioSource) was performed. The subjects underwent central Dual-Energy X-Ray Absorptiometry (DXA), which provided lumbar, femoral neck and total hip bone mineral density (BMD)/T-score (GE Lunar Prodigy), and lumbar DXA-based trabecular bone score (TBS iNsight). Results: We enrolled 89 females [mean age of 62.84 ± 9.33 years, average years since menopause (YSM) of 15.94 ± 9.23]. Irisin (102.69 ± 98.14 ng/mL) did not correlate with age, YSM, but with body mass index (r = 0.36, p < 0.001). Bone formation marker osteocalcin (r = −0.25, p = 0.018) was negatively associated with irisin, amidst multiple other mineral metabolism assays (including PTH and 25-hydroxyvitamin D). Irisin positively correlated with insulin (r = 0.385, p = 0.0008), HbA1c (r = 0.243, p = 0.022), and HOMA-IR (r = 0.313, p = 0.007). Additional endocrine assays pointed a statistically significant association between irisin and TSH, respectively, ACTH (r = 0.267, p = 0.01, and r = 0.309, p = 0.041, respectively). No correlation irisin-BMD/T-score/TBS was confirmed. Conclusions: Irisin correlates with markers of glucose status (insulin, HOMA-IR, and HbA1c), as well as body mass index and, to a lesser extent, bone metabolism markers. Interestingly, TSH and ACTH correlations open a new (hypothesis-generating) perspective in the endocrine frame of approaching this exerkine. To the best of our knowledge, no distinct study has so far addressed the TBS–irisin relationship or pinpointed the glucose effects on TBS, particularly in menopausal women.