There are really two separate questions here: 1. What do I do if the 4D CT scan does not show a parathyroid tumor? 2. Is this primary hyperparathyroidism or secondary?

For the first question: 4D CTs, or any other scan used to find parathyroid tumors, are not used to diagnose parathyroid disease or determine whether you need surgery. We use lab results to diagnose primary hyperparathyroidism and to determine who gets surgery. Since the only cure for primary hyperparathyroidism is surgery, if the diagnosis is clear then surgery is indicated, whether the scan shows anything or not. The diagnosis is determined with lab results: a high calcium and a normal or high PTH level indicates primary hyperparathyrodism. An experienced surgeon will be able to find the parathyroid glands, even without a scan showing where to go. Parathyroid tumors tend to be small, and may not ever show up on a scan. That does not prevent you from having surgery.

This brings us to the next issue, though, which is the diagnosis. Secondary hyperparathyroidism is a completely different disease from primary, and is usually not treated with surgery. A calcium level of 9.1 mg/dl with a PTH in the 90s indicates secondary hyperparathyroidism. The treatment for this is aggressive calcium and Vitamin D supplementation to get the calcium back into the mid to high 9s. Once the calcium rises, the PTH should drop back to normal range. Usually, just taking Vitamin D is not enough; some calcium supplements are necessary also.

In summary, the scan result does not determine whether you need an operation. That is dependent only on the diagnosis. The labs given here (calcium 9.1 and PTH 90s) indicate secondary hyperparathyrodism, not primary, and thus the treatment is calcium and Vitamin D supplementation.