Alterations in melatonin levels may relate to bone health in postmenopausal women with type 2 diabetes mellitus (T2DM). An observational study, published in Therapeutic Advances in Endocrinology and Metabolism, evaluated the association between serum melatonin levels and bone mineral density (BMD) in this population.

The analysis included 190 postmenopausal women who attended a clinic between September 2023 and September 2024. Participants were categorized into four groups: normal (n=45), abnormal bone mass (n=43), T2DM (n=46), and T2DM with abnormal bone mass (n=56). Glycolipid metabolism indices, bone metabolism markers, and melatonin levels were measured and analyzed.

Melatonin levels were lower in the abnormal bone mass, T2DM, and combined groups compared with the normal group [100.00 (94.00-110.00), 99.00 (91.75–100.25), and 92.50 (84.75-99.00) vs 127.71 (116.23-137.68); P<0.01], with the lowest levels observed in patients with both T2DM and abnormal bone mass. Melatonin levels showed positive correlations with lumbar spine (L1-L4) BMD and femoral neck BMD.

T2DM showed site-specific mediation effects. It did not significantly mediate the association between melatonin and lumbar spine BMD (−8.16%, 95% CI −90.39 to 57.00), but accounted for 33.95% (95% CI 5.38–70.00) of the association with femoral neck BMD. Receiver operating characteristic analysis showed strong diagnostic performance of melatonin for osteoporosis, with an area under the curve of 0.942 (95% CI 0.902-0.982). The optimal cut-off value was 124.29 pg/mL, with a sensitivity of 57.8% and a specificity of 99.3%.

Multiple linear regression analysis identified decreased melatonin levels as a risk factor for reduced BMD. These findings indicate that lower serum melatonin levels are associated with decreased BMD in postmenopausal women with T2DM and may have diagnostic value for abnormal bone mass in this population.