Normal level of calcium in the blood.
Explanation:
The normal range of PTH levels means that there is normal amount of calcium is present in the blood. If the PTH level is too high it means that the levels of calcium in the blood is very low while on the other hand, if the levels of PTH is low it means that the level of calcium in the blood is too high so that's why normal range of PTH level means normal level of calcium in the blood.