Endocrine Abstracts

Background: X-linked hypophosphatemia is a captivating yet challenging disorder that leads to rickets, skeletal deformities, osteomalacia, and impaired growth due to elevated levels of fibroblast growth factor 23 and subsequent hypophosphatemia. Traditionally, managing this condition has involved high doses of phosphate salts and vitamin D.

Case Report: Startlingly, we document a case presenting X-linked hypophosphatemic rickets caused tertiary hyperparathyroidism, in a patient, regardless of phosphate and vitamin D replacement. X-linked dominant hypophosphatemic rickets (XLHR) is a metabolic bone syndrome, hereditary in nature, relatively infrequent with progression to developing irreversible tertiary hyperparathyroidism. Tertiary hyperparathyroidism (TH) is recognized as an unusual complication associated with XLHR observed in patients undergoing the treatment of phosphate and calcitriol. In 2019, an MIBI scan and 4D CT parathyroid excluded the presence of adenoma or parathyroid hyperplasia, prompting the surgical removal of all four parathyroid glands to address tertiary hyperparathyroidism, which subsequently normalized calcium levels. Histological analysis confirmed parathyroid hyperplasia. However, in 2022, the patient again developed hypercalcemia and elevated PTH levels. A follow-up MIBI scan identified a rare 12 mm hyperplastic parathyroid nodule within the soft tissues of the neck. This raised a serious concern in parathyroid multidisciplinary team meetings regarding surgery, as its execution might not work again and the patient would develop parathyroid nodules, again. Currently, Burosumab, a human anti-FGF23 monoclonal antibody is in consideration to be administered with calcimimetic like cinacalcet - that will be licensed in the UK from August 7, 2024 – to manage the complications.

Conclusion: This case highlights the urgent necessity for alternative treatments for XLHR patients who have had minimal success or adverse reactions to phosphate/calcitriol therapy. We advocate for more comprehensive research to help the scientific community reach a consensus on whether surgical intervention or the use of various effective agents, such as Burosumab, should be prioritized for managing tertiary hyperparathyroidism.