An instrument for therapeutically cytotoxically ablating parathyroidal tissue is disclosed. A substance is capable of transforming the parathyroid gland from overproduction of parathyroid hormone when the substance's quantity exceeds a set amount, and is capable of transforming the parathyroid gland from overproduction only when activated by application of sufficient units of an electromagnetic energy having a frequency ranging from 400 THz to 30 PHz when the substance's quantity is below the set amount. A delivery device is operable to introduce the substance into the parathyroidal tissue and to quantitatively limit the quantity to below the set amount. An energy device is operable to apply units of the electromagnetic energy after the substance has been introduced. A sensor is operable to monitor the activation of the substance as the electromagnetic energy is applied. The energy device is further operable to modulate applying the electromagnetic energy when the substance has been activated.