ACTA ENDOCRINOLOGICA (BUC)

Pituitary stalk interruption syndrome (PSIS) is characterized by the coexistence of an absent or thin pituitary stalk, an ectopic posterior pituitary (EPP) lobe, and an absent or hypoplastic anterior pituitary lobe. A 1-year-old boy presented with micropenis, and undescended testis associated with growth hormone, thyroid stimulating hormone, and gonadotropin deficiencies. Pituitary hypoplasia, EPP, and a missing pituitary stalk were seen on magnetic resonance imaging (MRI). Whole-exome sequencing (WES) revealed compound heterozygous variants in the KATNIP gene (NM_0.15202.5: c1461G>A / c.4035delC) in the recruited individual, and subsequent familial segregation showed that family established the trans position for c.1461G>A and c.4035delC variants.

Denosumab,a monoclonal IgG2 antibody directed against RANK-L,is used as a neoadjuvant therapy for inoperable or metastatic giant cell tumor of bone. Many side effects like as hypocalcemia during treatment and rarely severe hypercalcemia especially in children after discontinuation of denosumab occurred. The unpredictable onset and recurrent episodes of severe hypercalcemia increase the duration of hospitalization and the risk of complications. Persistent hypercalcemia and difficulties in management have prompted the search for different more effective therapeutic options. Objectives. To share our experience with the use of oral bisphosphonate in acute and long-term therapy of severe hypercalcemia following high-dose denosumab therapy and to review the literature on this subject Case. We report the management of a case of severe hypercalcemia that developed 4 months after the completion of 18-month denosumab treatment in a 9-year-old girl who was followed up with a giant cell bone tumor for 6 years. Based on an evaluation aiming to determine etiology, hypercalcemia was considered as "rebound-linked" upon denosumab discontinuation. Severe hypercalcemia attacks recurring with an interval of 2 weeks were treated with IV bisphosphonate, but when mild hypercalcemia developed again, treatment with 70 mg per week of oral bisphosphonate was planned. After the second dose of alendronate, the calcium level always remained below 10.5 mg/dl. In the 14-month follow-up, no hypercalcemia attack was observed again. Results. Rebound hypercalcemia can occur as an unpredictable recurrent episode at any time after denosumab cessation. Thus, the patient should be closely monitored especially in childhood due to rapid bone cycle. In longterm follow-up, oral biphosphonates can be used effectively to reduce hospitalization time and the management of especially life-threatening recurrent attacks.

Denosumab,a monoclonal IgG2 antibody, is used as neoadjuvant therapy for giant cell bone tumors, particularly in inoperable or metastatic cases. It targets the receptor activator of nuclear factor kappa-β ligand (RANKL), which is overexpressed in tumor stromal cells. However, denosumab treatment can lead to side effects such as hypocalcemia during treatment and rarely but malignant hypercalcemia after discontinuation. The unpredictable onset time and persistent course of hypercalcemia attacks increase the duration of hospitalization and the risk of complications. Case. A 9-year-old girl with a giant cell bone tumor was treated with denosumab for diffuse tumor recurrence. Severe hypercalcemia occurred four months after completing therapy. Evaluation suggested "rebound-linked" hypercalcemia following denosumab discontinuation. IV bisphosphonate treatment normalized calcium levels initially, but hypercalcemia recurred, requiring repeated IV bisphosphonate administration. Oral alendronate was used weekly to prevent further attacks, resulting in stable calcium levels during follow-up. Results. Rebound hypercalcemia, as an unpredictable recurrent episode at any time, is a potential complication of denosumab cessation, and requires close monitoring post-treatment. Children may be at higher risk due to their rapid bone cycle. In long-term follow-up, IV and oral bisphosphonates can be used effectively in the management of especially life-threatening recurrent attacks.