Three years ago I had a parathyroid tumor removed. I did very well, but recently my PTH has gone up to 85 pg/ml (normal range up to 65 pg/ml). Do I have another parathyroid tumor? My last calcium was 9.1 mg/dl.
Your labs are now more consistent with secondary hyperparathyroidism (not primary hyperparathyroidism, which is what you had three years ago). That is, the parathyroid glands are making more hormone in response to a low calcium level. Ideally you want your calcium level to be closer to the mid to high 9s in mg/dl. Your remaining parathyroid glands are doing exactly what we want them to do when the calcium is low.
We treat this with calcium and Vitamin D supplementation. Vitamin D helps the intestines absorb calcium. Once your calcium level is a little higher, the PTH should drop back down to normal range.