What is one of the actions of parathyroid hormone related to calcium?

The action of parathyroid hormone (PTH) that is relevant to calcium metabolism includes transferring calcium from bone to blood, which is indeed the correct answer. PTH is secreted by the parathyroid glands in response to low blood calcium levels. One of its primary functions is to stimulate osteoclast activity in bones, leading to the resorption of bone tissue. This process releases stored calcium into the bloodstream, effectively raising serum calcium levels.

This mechanism plays a critical role in maintaining calcium homeostasis in the body. When calcium levels are low, the regulation via PTH helps ensure that there is an adequate supply of calcium in the blood to support various physiological processes, including muscle contraction, nerve transmission, and blood clotting.

While there are other hormones and mechanisms involved in calcium metabolism, such as vitamin D enhancing intestinal calcium absorption and the kidneys reabsorbing calcium, these are not direct actions of PTH itself but rather part of the broader regulatory system for calcium balance.