Endocrine Abstracts

Background: Malignant hypercalcemia (MH) occurs in up to 30% of patients who are diagnosed with cancery, being associated with later stages of the disease and poor prognosis. The physiopathological mechanisms responsible for MH are the production of parathyroid hormone-related peptide by the tumor (PTHrp) (80% of cases), osteolytic cytokine production (20%) and excess of 1,25(OH)₂vitamin D production (1%).

Case report: We present the case of a 60-year-old man diagnosed, after an increase in scrotal and abdominal volume, with a 25 cm retroperitoneal mass suspicious for liposarcoma. Preoperatively, a hypercalcemia of 16.3 mg/dl was detected, with a serum phosphorous of 6.3 mg/dl and an acute renal failure. He was referred to our department and immediately started intensive fluid replacement, loop diuretics and glucocorticoids. From the initial investigation: PTH <3.0 pg/ml, 25(OH)vitamin D 18 ng/ml, alkaline phosphatase 91 UI/l, PTHrp < 0.5 pmol/l and 1,25(OH)₂vitamin D 224 pg/ml (18–71). He also did a bone scan scintigraphy that was negative for metastases and multiple myeloma was excluded. He was discharged from hospital but was again readmitted 15 days later with serum calcium of 19.2 mg/dl. Since bisphosphonate treatment was contraindicated, denosumab 120 mg was administered at day 1, 8, 15 and 29, with a good response (calcium of 11.5 mg/dl). After surgery, hypercalcemia completely resolved, with serum calcium levels between 8 and 9 mg/dl and normalization of 1,25(OH)₂vitamin D (54 pg/ml).

Conclusion: Malignant hypercalcemia due to tumoral production of 1-alpha-hydroxylase with excess of conversion of 25(OH)vitamin D to 1,25(OH)₂vitamin D is extremely rare. Most of the reported cases are associated with granulomatous diseases like sarcoidosis and, less frequently, with Hodgkin’s Lymphoma or ovarian dysgerminoma. In summary, to the best of our knowledge, we report the first case of extrarenal production of 1,25(OH)₂vitamin D associated to abdominal sarcoma in the literature.