The diagnosis is made by proving the biochemical abnormality.
The physician should obtain more than one sample of blood for calcium and parathyroid hormone (PTH). The patient should have normal kidney function. A positive test would show raised calcium levels and an inappropriate PTH. In non-parathyroid causes of high calcium levels the PTH level in the blood is low.
PTH assays are discriminating and there are few situations where a raised PTH does not indicate true primary hyperparathyroidism. One exception is familial benign hypercalcaemia. This is a rare cause of raised serum calcium that runs in families and does not need parathyroid surgery. In this condition the parathyroid calcium sensor is incorrectly set. The calcium levels are rarely very high and there is very little calcium in the urine, allowing the experienced clinician to differentiate it from primary hyperparathyroidism.
Before any surgery is performed, if indeed it is indicated, the tumour secreting the excess PTH will have to be localised. Techniques for doing this are described in the section 'Surgery - Tests required prior to operation'.