Parathyroid Hormone (PTH) is a critical regulator of calcium and phosphate metabolism in the body, primarily increasing blood calcium levels by stimulating osteoclast activity, enhancing renal tubular reabsorption of calcium, and promoting the activation of vitamin D in the kidneys. Imbalances in PTH secretion can lead to conditions such as hyperparathyroidism or hypoparathyroidism, affecting bone health and calcium homeostasis.