The parathyroid glands are small, pea-sized glands located behind the thyroid gland in the neck. Typically, there are four of these glands, and they play a crucial role in regulating the body's calcium levels. They produce a hormone called parathyroid hormone (PTH), which helps control the amount of calcium in the blood and bone. When calcium levels drop, the parathyroid glands release PTH, which increases calcium levels by promoting its release from bones, enhancing absorption in the intestines, and reducing its loss in urine. This regulation is vital for maintaining healthy bones and proper functioning of the nervous and muscular systems.