Which statement about primary hypoparathyroidism is true?

Which statement about primary hypoparathyroidism is true?

• A. PTH is low
• B. PTH is high
• C. PTH is normal
• D. PTH varies

Answer: (A)

In primary hypoparathyroidism, the parathyroid glands fail to produce sufficient parathyroid hormone. Since PTH is the hormone that raises blood calcium by acting on bone, kidneys, and the gut (via active vitamin D), its deficiency leads to low calcium levels. At the same time, phosphate is not adequately excreted by the kidneys, so phosphate tends to be elevated. This pattern—hypocalcemia with a low, inappropriately low or absent PTH level after a calcium check—defines primary hypoparathyroidism. The other scenarios, where PTH is high or normal, point to secondary causes or resistance rather than a primary gland failure, making the statement that PTH is low the correct one.

In primary hypoparathyroidism, the parathyroid glands fail to produce sufficient parathyroid hormone. Since PTH is the hormone that raises blood calcium by acting on bone, kidneys, and the gut (via active vitamin D), its deficiency leads to low calcium levels. At the same time, phosphate is not adequately excreted by the kidneys, so phosphate tends to be elevated. This pattern—hypocalcemia with a low, inappropriately low or absent PTH level after a calcium check—defines primary hypoparathyroidism. The other scenarios, where PTH is high or normal, point to secondary causes or resistance rather than a primary gland failure, making the statement that PTH is low the correct one.