Autonomous hyperparathyroidism following long-term phosphate treatment for tumor-induced osteomalacia - Case report and review of the literature

Development of secondary or even tertiary hyperparathyroidism following phosphate administration is an established complication in patients with X-linked hypophosphatemic rickets. However, in tumor-induced osteomalacia (TIO) there are very few documented cases of hyperparathyroidism persisting even after excision of the tumor (tertiary hyperparathyroidism). The development of hyperparathyroidism in TIO is related to long-term phosphate administration, which represents the main treatment option in cases of unlocalized or non-excisable tumors. Furthermore, low or inappropriately normal calcitriol levels either systemically or at the level of parathyroid cell are probably implicated in parathyroid tumorigenesis. We present a case of a 68-year-old female patient with TIO who received long-term phosphate treatment prior to localization and excision of the tumor and afterward developed autonomous hyperparathyroidism.