According to the HORRIBLE endocrinologist I saw (waiting for an appointment with a better one) there are several reasons for calcium to be elevated. Hyperparathyroidism, hyperthyroidism, benign tumor in the lungs, and if it's REALLY HIGH it could be a cancer. Definitely see an endocrinologist if you haven't already. I'm still trying to find the reason for my own hypercalcemia - though the tests so far don't point to cancer.

Familial hypocalciuric hypercalcemia is my diagnosis. It's genetic and very rare. My calcium is very high. I am prescribed large doses of vitamin d. No other options for me, since it's not my thyroid.

i had hyperparathyroidism from my kidneys failing so i was put on a medication to help lower it which worked really well. however this medication and another were both calcium based and my calcium skyrocketed. i did have the option of removing some of my pth glands but then i had my transplant scheduled. i still have a bit of high pth and calcium so i just take a large dose of vitamin d every week. it’s helped a lot and now i’m even allowed tums!