Final answer:
Parathyroid hormone (PTH) secretion is stimulated by low blood calcium levels. PTH enhances calcium reabsorption by the kidneys, stimulates osteoclast activity, and inhibits osteoblast activity. PTH also stimulates the synthesis and secretion of calcitriol, which enhances calcium absorption by the digestive system.
Step-by-step explanation:
Parathyroid hormone (PTH) secretion is stimulated in response to low blood calcium levels. When calcium ion levels fall below normal, PTH is produced and released by the parathyroid glands. PTH has several effector functions, including enhancing reabsorption of calcium by the kidneys, stimulating osteoclast activity, inhibiting osteoblast activity, and stimulating the synthesis and secretion of calcitriol, which enhances calcium absorption by the digestive system.