Hypocalcemic Crisis Induced by Excessive Milking Running Title: Milking-Induced Hypocalcemic Crisis

Background: Calcium loss by lactation does not cause hypocalcemia unless mothers have subclinical hypoparathyroidism. Case report: A 32-year-old woman was an inhabitant of an island located in the south-western region of Japan. She delivered her second boy by Caesarian section in 37th week of gestation in a hospital in the mainland. She began milking the breasts 6 to 7 times a day, yielding ca. 200 ml each times, on 4th post-operative (henceforth, PO day). She left her baby in the hospital and returned her home island on the 7th PO day. Then, she continued milking the breasts daily and shipped milk to the hospital for her baby. On the 13th PO day, she noticed paresthesia around the mouth and in both hands. Following day, she was admitted in author’s hospital for hypocalcemic crisis with intermittent carpopedal spasm and opisthotonos on rare occasions. The initial blood study revealed serum albumin 3.4 g/dl, calcium 4.6 mg/dl (reference range, 8.6-10.2), inorganic phosphate 1.6 mg/ dl (reference range, 1.7-2.6). She was given i.v. injections of 8.5% calcium gluconate, 10 ml and 20 ml successively, which was followed by continuous i.v. infusion of calcium-enriched saline until the 15th PO day. Serum calcium normalized after cessation of milking. Serum intact parathyroid hormone level was 153 pg/ml (reference range, 10-65) at the time of the admission. Conclusion: The amount of milk mother produces is determined by baby’s sucking. When mother is separated from her baby, she might milk the breasts more than the baby’s need. Excessive milking has conceivably precipitated hypo-calcemic crisis in the present patient.