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PTH enhances calcium absorption from the bone through two mechanisms.It is noteworthy that mature osteoclasts do not have receptors for parathyroid hormone (PTH); they are stimulated to activate and grow by cytokines from activated osteoblasts and osteocytes, or by immature osteoclast precursors with PTH and vitamin D receptors undergoing differentiation.[3]Kidney function involves PTH inhibiting phosphate reabsorption in the proximal tubule and enhancing calcium reabsorption in the ascending loop of Henle, distal tubule, and collecting tubule.When the parathyroid hormone (PTH) attaches to receptors on these cells, the osteocytic membrane shifts calcium ions from the bone fluid to the extracellular fluid.

‏ The main reaction of the kidney to parathyroid hormone (PTH) is to boost the absorption of calcium and the excretion of phosphate. Kidney function involves PTH inhibiting phosphate reabsorption in the proximal tubule and enhancing calcium reabsorption in the ascending loop of Henle, distal tubule, and collecting tubule. [3]

PTH enhances calcium absorption from the bone through two mechanisms. The quick stage results in a quick increase in blood calcium levels within minutes and seems to happen at the osteoblasts and osteocytes. Even though it may appear contradictory, the cells that encourage bone formation also play a role in bone breakdown, creating an interconnected network called the osteocytic membrane on top of the bone matrix, separated by a thin layer of fluid known as bone fluid. When the parathyroid hormone (PTH) attaches to receptors on these cells, the osteocytic membrane shifts calcium ions from the bone fluid to the extracellular fluid. [3]

Bone resorption's gradual phase takes place over a few days and consists of two parts. Initially, osteoclasts are stimulated to break down developed bone, and subsequently, there is an increase in osteoclasts. It is noteworthy that mature osteoclasts do not have receptors for parathyroid hormone (PTH); they are stimulated to activate and grow by cytokines from activated osteoblasts and osteocytes, or by immature osteoclast precursors with PTH and vitamin D receptors undergoing differentiation.[3]