What increases reabsorption of Ca plus 2 by the kidneys?

Reabsorption of calcium ions (Ca²⁺) by the kidneys is primarily increased by parathyroid hormone (PTH), which promotes calcium reabsorption in the renal tubules. Additionally, vitamin D enhances calcium reabsorption by increasing the expression of calcium transport proteins. Other factors, such as low serum calcium levels and certain renal conditions, can also stimulate increased reabsorption of calcium.