Which hormones help maintain a relatively constant calcium concentration in the blood?

The primary hormones that help maintain a constant calcium concentration in the blood are parathyroid hormone (PTH) and calcitonin. PTH, produced by the parathyroid glands, increases blood calcium levels by promoting bone resorption, enhancing intestinal absorption, and reducing renal excretion of calcium. Conversely, calcitonin, produced by the thyroid gland, lowers blood calcium levels by inhibiting bone resorption and promoting calcium excretion in the kidneys. Together, these hormones regulate calcium homeostasis in the body.