Hyperparathyroidism is a condition where your parathyroid gland is releasing too much parathyroid hormone. If too much parathyroid hormone is being released, the levels of calcium in your blood become too high. Parathyroidectomy is an operation to remove one or more of your parathyroid glands. Parathyroidectomy is normally used to treat hyperparathyroidism. Parathyroidectomy is also used to treat tumours of the parathyroid glands.