What else could cause elevated pth but normal calcium other than parathyroid?

Kidney Failure: Kidney failure is another cause of secondary hyperparathyroidism. When kidneys are not working well, phosphorus levels go up, and calcium levels go down. These lower calcium level stimulate the parathyroids to make more pth. Again, even if the calcium levels are in the normal range, they may be low for that person, and cause the PTH to go up.

Low Vitamin D: Low vitamin d can cause secondary hyperparathyroidism (high PTH level due to something outside of the parathyroid gland). Low vitamin d levels can make someone's calcium lower than it should be (even if it's still in the normal range). The parathyroid glands make more PTH to try to get the calcium back up where it should be.