We present a case of severe hypercalcemia in a 53-year-old woman, initially suggestive of primary hyperparathyroidism due to non-suppressed intact parathyroid hormone (PTH) levels and unilateral intrathyroidal tracer uptake on a technetium 99m sestamibi parathyroid scan. The gene discussed is PTH; the disease is primary hyperparathyroidism.