Final answer:
Persistent HPTH after correction of secondary HPT is due to autonomous PTH secretion that is unresponsive to normal negative feedback due to elevated calcium levels.
Step-by-step explanation:
Elevated calcium levels can lead to persistent hyperparathyroidism (HPTH) after correction of secondary HPT. In this condition, the parathyroid glands continuously secrete parathyroid hormone (PTH) even though calcium levels are already high, indicating a failure of normal negative feedback. This unresponsiveness to feedback is due to autonomous PTH secretion.
For example, when blood calcium levels rise, normally PTH secretion would decrease to inhibit further calcium release from the bones. However, in autonomous PTH secretion, the parathyroid glands do not sense the elevated calcium levels and continue to release PTH, which can result in elevated calcium levels in the blood.