The parathyroid hormone (PTH) test is a laboratory examination that measures the level of parathormone produced by the parathyroid glands in the blood to assess calcium and phosphorus balance. PTH is an important hormone responsible for regulating calcium and phosphorus levels in the body. This test determines the current level of PTH. The normal reference range is typically 15-65 pg/mL, and levels that are low or high may indicate various health issues.