Which of the following conditions will stimulate parathyroid glands to release PTH?

Fall in blood Ca²⁺ levels stimulates the parathyroid gland to release parathyroid hormone. The parathyroid gland is responsible for producing and releasing parathyroid hormone (PTH), which plays a crucial role in regulating calcium homeostasis in the body. When blood calcium levels drop below normal, the parathyroid gland is stimulated to release PTH. PTH promotes the release of calcium from bones, enhances calcium reabsorption in the kidneys and stimulates the production of active vitamin D, which increases intestinal absorption of calcium.

A rise in blood calcium levels stimulates the release of thyrocalcitonin. A fall in blood glucose levels stimualtes the release of glucagon. A rise in blood glucose levels stimulates the release of insulin.