Systems Pathology Exam 1 Practice

End-organ resistance to parathyroid hormone is the key idea. In pseudohypoparathyroidism, the parathyroid glands release plenty of hormone, but the kidneys and bones don’t respond due to a defect in PTH signaling. Because the target tissues don’t react, calcium stays low despite high PTH, and phosphate tends to be elevated since the kidney can’t excrete it effectively. The body keeps secreting more PTH in an attempt to raise calcium, so PTH remains high even though calcium remains low. This pattern—high PTH with hypocalcemia from receptor signaling failure—fits pseudohypoparathyroidism rather than other forms of hyperparathyroidism, where calcium levels would differ (primary hyperparathyroidism usually raises calcium; secondary hyperparathyroidism often has low or normal calcium with compensatory high PTH).