Yes, observational research suggests that cycling can reduce bone density most likely because cycling is a non-weight-bearing exercise . Studies have found that two-thirds of professional cyclists had abnormally low bone mineral density (BMD) values, and riders who train between 3-8 hours a week have similar results . Combining cycling with load-bearing exercise such as running, weight training, tennis, and hiking may help offset the impact of biking on bone health .
 Olmedillas, H., González-Agüero, A., Moreno, L. A., Casajus, J. A., & Vicente-Rodríguez, G. (2012). Cycling and bone health: a systematic review. BMC Medicine, 10(1). https://doi.org/10.1186/1741-7015-10-168
 Medelli, J., Lounana, J., Menuet, J. J., Shabani, M., & Cordero-MacIntyre, Z. (2009). Is osteopenia a health risk in professional cyclists?. Journal of clinical densitometry : the official journal of the International Society for Clinical Densitometry, 12(1), 28–34. https://doi.org/10.1016/j.jocd.2008.07.057