Extremely High Preoperative Parathyroid Hormone Associated With Severe Postoperative Hungry Bone Syndrome-Induced Delirium in a Case of Parathyroid Carcinoma in Vietnam: A Case Report.

Parathyroid carcinoma (PC) is one of the rarest cancers, accounting for less than 1% of all cases of primary hyperparathyroidism worldwide. The preoperative level of parathyroid hormone (PTH) has been taken as an essential index in diagnosing and prognosting PC. The conventional range of preoperative PTH was three to 10 times higher than the upper limit. Recently published studies have shown a significantly extensive range of preoperative levels of PTH in different countries, which might change our opinion on probable preoperative PTH levels in PC and its related postoperative complications. We present a case of a 47-year-old Vietnamese male patient suffering from PC with preoperative PTH up to 60 times higher than the upper limit. After the surgery, the patient developed hungry bone syndrome (HBS), manifesting through severe hypocalcemia at 0.04 mmol/l of ionized calcium, which altered his mental status for one week and required a hefty dose of calcium to normalize the patient's plasma calcium levels. There seems to be no upper limit for PTH levels in PC. A significantly high level of preoperative PTH is an essential warning sign of severe HSB developing postoperatively.