Calcitonin and Parathyroid Hormone

Question

Calcitonin and parathyroid hormone
A) are both secreted by the parathyroid glands.
B) increase plasma levels of calcium.
C) decrease plasma levels of calcium.
D) control plasma levels of calcium.

Accepted Answer

Calcitonin and parathyroid hormone have opposing effects on plasma levels of calcium. Calcitonin decreases plasma levels of calcium, while parathyroid hormone increases plasma levels of calcium. Together, they help control plasma levels of calcium. However, only parathyroid hormone is secreted by the parathyroid glands, not calcitonin. Therefore, the correct answer is D, which states that calcitonin and parathyroid hormone control plasma levels of calcium.