We describe a unique case of hyperphosphatemia associated with a very high bone turnover rate in a 51-year-old postmenopausal woman with undiagnosed anorexia nervosa (AN) who presented with a low-trauma hip fracture. In view of her severely malnourished state, she was not fit for surgery. She was treated according to a refeeding protocol that mandated bed rest. Contrary to expectation, she developed sustained hyperphosphatemia and borderline hypercalcemia. Bone remodelling markers, both resorption and formation, were markedly elevated. Parathyroid hormone (PTH) was low-normal at 1.7 pmol/L, C-terminal fibroblast growth factor 23 (FGF23) was high at 293 RU/ml, but tubular maximum reabsorption of phosphate (TmPO4/GFR) was elevated at 1.93 mmol/L. Denosumab 60 mg was administered that was followed by: rapid normalisation of serum phosphate; normalisation of resorption markers, transient hypocalcaemia with secondary hyperparathyroidism, and normalisation of both TmPO4/GFR and C-terminal FGF23. We speculate that prolonged immobilization as part of AN management led to a high remodelling state followed by hyperphosphatemia and high-normal calcium with appropriate suppression of PTH and that marked hyperphosphatemia and high TmP/GFR despite high FGF23 indicates the necessity of PTH adequacy for excess FGF23 to lower TmP/GFR.

我们描述了一个高磷酸盐血症的独特案例，该案例与一名51岁绝经后女性，未确诊的神经性厌食症（AN）伴低创伤性髋部骨折的高骨转换率相关。鉴于她的严重营养不良状况，她不适合手术。根据要求卧床休息的再喂养方案对她进行了治疗。与预期相反，她发展为持续性高磷酸盐血症和临界高钙血症。吸收和形成的骨重塑标志物均显着升高。甲状旁腺激素（PTH）为低正常值，为1.7 pmol / L，C端成纤维细胞生长因子23（FGF23）高，为293 RU / ml，但肾小管中最大的磷酸盐重吸收（TmPO4 / GFR）为1.93 mmol / L。 L. 给予Denosumab 60 mg，随后进行：血清磷酸盐快速正常化；吸收标记正常化，继发性甲状旁腺功能亢进引起的短暂性低钙血症以及TmPO4 / GFR和C端FGF23均正常化。我们推测，作为AN管理的一部分，长期固定会导致高重塑状态，然后出现高磷酸盐血症和高正常钙，并适当抑制PTH；尽管FGF23较高，但仍有明显的高磷酸盐血症和高TmP / GFR，这表明PTH对于过量FGF23的充分性是必要的降低TmP / GFR。