Final answer:
Parathyroid hormone (PTH) promotes the reabsorption of calcium by the kidney tubules, helping regulate blood calcium levels.
Step-by-step explanation:
The hormone responsible for promoting the reabsorption of calcium by the kidney tubules is parathyroid hormone (PTH). PTH is released by the parathyroid glands when blood calcium levels fall below normal. Its actions include stimulating osteoclast activity in bones to release calcium into the bloodstream, increasing calcium reabsorption in the kidneys, and triggering the production of the active form of vitamin D, calcitriol, which further aids in calcium absorption from the diet.