PTH and hypoparathyroidism: In addition to decreased PTH secretion, which may be related to hypoparathyroidism, due to the removal of the parathyroid glands during surgery for the thyroid or the parathyroid, hypocalcemia may be caused by chelation with phosphates, anticoagulants (e.g., citrate, EDTA) and free fatty acids from acute pancreatitis as well as extensive osteoblastic metastases and sepsis.