The primary role of the parathyroid glands in calcium regulation is to maintain optimal levels of calcium in the blood. They achieve this through the secretion of parathyroid hormone (PTH), which increases blood calcium levels by stimulating the release of calcium from bones, enhancing intestinal absorption of calcium, and promoting renal reabsorption. This delicate balance is essential for various bodily functions, including muscle contraction, nerve function, and blood clotting. Dysfunction in parathyroid hormone regulation can lead to conditions such as hyperparathyroidism or hypoparathyroidism.