Parathyroid hormone (PTH) is a hormone produced by the parathyroid glands, which are small glands located in the neck behind the thyroid gland. PTH plays a crucial role in regulating the body's calcium levels by increasing the concentration of calcium in the blood. It does this by stimulating the release of calcium from bones, enhancing calcium absorption in the intestines, and promoting the reabsorption of calcium in the kidneys. When calcium levels in the blood drop, the parathyroid glands release more PTH to restore balance. Conversely, when calcium levels are high, PTH secretion decreases. This regulation is essential for maintaining healthy bones and overall bodily functions, as calcium is vital for muscle contraction, nerve function, and blood clotting.