Can Low Calcium Levels Be Related To Osteopenia?

I have had 2 low calcuim blood tests in the past month, doctor has now requested PTH and vit D blood test, which I am wating on results, last year a dexa scan confirmed I had osteopenia are they related ? I am 31 years old, lady, non smoker, para 2+0 5 foot 5, white caucasin