Hi @closetmonster93 - Hypercalcemia with osteoporosis screams primary hyperparathyroidism. While there are other causes you need to check out, the odds are here.

I put together a video segment on hyperparathyroidism based on Dr. John Bilezikian, who is a top osteoporosis doctor. You can watch the segment here https://youtu.be/xKNdqISXkFY?si=80l-T3gQ7iDvVxMw&t=2205 . The entire video should be helpful but this link is to the segment on hyperparathyroidism.