The most popular HIV drug increases parathyroid hormone which leaches bones. Vitamin D reverses this

[Nelson Vergel]

Tenofovir can increase PTH (Abacavir did not) which can cause bone loss.

Early changes in parathyroid hormone concentrations in HIV-infected patients initiating... - Abstract - Europe PubMed Central


If you take Vitamin D, this may be reversed:


Vitamin D3 Decreases Parathyroid Hormone in HIV-Infected Youth Being Treated With Tenofovir: A Randomized, Placebo-Controlled Trial