Bone Density Loss for PrEP Users?

A new study of a small group of young men who have sex with men taking PrEP (Pre-exposure Prophylaxis) to prevent HIV infection has raised concern that the drug may be fueling loss of bone mineral density.
"Through 48 weeks, BMD dropped about 1 percent at the hip and about 0.6 percent in the whole body but not in the spine," reported Mark Mascolini in the conference reports for the 18th International Workshop on Comorbidities and Adverse Drug Reactions in HIV. "Percent changes in spine and hip BMD at week 48 correlated with tenofovir diphosphate levels in blood cells."
The average of age of the MSM studied was 20, and 46.5 percent of participants were African-American and 26.5 percent Latino; 79 percent of men identified themselves as gay and 14 percent as bisexual. Most of those enrolled started the study with "below normal" bone mineral density before beginning PrEP.
When the participants stopped using PrEP, the bone mineral density loss was reversed. However, it remains unclear if Truvada, the only drug approved for PrEP in the U.S., was responsible for the loss during drug use, or if nutritional and other factors played a role.
Investigators said the findings "suggest" some impact on bone growth in youth on PrEP.