Background: Melatonin is known for its regulation of circadian rhythm, however, over recent years, studies have shown that melatonin also has a positive effect on bone. With age, the melatonin levels decrease leading to further imbalanced bone remodelling. We aimed to investigate whether treatment with melatonin may improve bone parameters.
Method: In a double-blind placebo-controlled investigator initiated study, we randomised 81 healthy post-menopausal women with osteopenia to 1-year of treatment with melatonin in a nightly dose of 1 mg (n=20), or 3 mg (n=20), or similar placebo (n=41). At baseline and after 12 months of treatment, DXA measurements of body composition, and BMD at the spine and hip were collected. Biochemical markers of calcium homeostasis were measured throughout the trial.
Results: Mean age was 63 (range 5673) years. Compared with placebo, BMD at the femoral neck increased by 1.4% (95% CI: −2.7; −0.0, P<0.05) in response to melatonin. A dose-response relationship was present (P<0.01) as BMD at the femoral neck increased by 2.3% (95% CI: 0.7; 4.0, P<0.01) in the high dose (3 mg/day) melatonin group compared with placebo. Compared with 1 mg/d of melatonin, BMD in the 3 mg/d group increased by 1.9% (95% CI: 0.0; 3.7, P<0.05). Treatment did not affect BMD at other skeletal sites or levels of bone turnover markers, however, there was a significant decrease in 24 h urinary calcium in the melatonin group (−3.7%, IQR: −2.9; 57.0) compared with placebo (8.5%, IQR: −11.5; 19.4, P=0.02). Moreover, compared with placebo, melatonin decreased fat mass significantly by 6.8% (95% CI: 1.3; 12.3, P=0.02), while lean body mass increased by 2.2% (95% CI: −4.8;0.3, P=0.08).
Conclusion: One year of treatment with melatonin improved BMD dose-dependently at femoral neck and showed beneficial effects on body composition in terms of a reduced fat mass and borderline increased lean tissue. Further studies are needed to assess mechanisms of action and whether night-time melatonin may protect against fractures.
Disclosure: The authors declared no competing interests.