Calcitriol Induced Hyper Calcemia in Stroma Uterine Cancer Independent From PTHrp

Case Presentation: A 70-year-old female with a history of breast cancer presented with an intra-abdominal mass. The biopsy of the mass was positive for endometrial stromal sarcoma. During hospital admission, the patient was noted to have hypercalcemia attributable to her malignancy. This hypercalcemia responded positively with IV fluids with calcitonin, and the patient was discharged with oncology follow-up for chemotherapy. The patient was referred back upon repeat labs by oncology showing a calcium of 13.4 mg/dL. The physical exam at this time was unremarkable. However, labs were significant for a RDW of 16.7%, Monocyte count of 17.7 mcg/L, Creatinine of 1.24 mg/dL, Calcium of 12.8 mg/dL, and Globulin of 4.2 g/dL. Special chemistry tests came back significant for a 1,25 Dihydroxy Vitamin D level of 256.8 pg/mL, PTHrP level of 3.7 pmol/L, PTH of 18.6 pg/mL, and free kappa light chains of 47.18 mg/dL. The patient was then placed on Prednisone 20mg daily with Zometa as needed with GYN oncology follow-up. Discussion: Paraneoplastic hypercalcemia is a relatively common finding in malignancy, affecting up to 44% of patients (Mirrakhimov, 2015). However, the etiology behind hypercalcemia ranges from increased PTHrP, osteolytic metastases, parathyroid related tumors, and uncommonly from 1,25 Hydroxy Vitamin D (Mirrakhimov, 2015). The patient presented with hypercalcemia secondary to an endometrial stromal sarcoma. The hypercalcemia was presumed to be related to PTHrP, however, serum levels of PTHrP and PTH were at the upper limits of normal, thus not sufficient to explain hypercalcemia. The elevated Vitamin D level was suspect for a calcitriol mediated hypercalcemia, a rare finding with a few case reports relating to gastrointestinal stromal tumors (Betlachin, Kim, & Oxman, 2020). The diagnosis is further backed up by the patient’s response to prednisone, which reduces 1 alpha hydroxylase activity, reducing the calcium levels. Calcitriol mediated hypercalcemia is a phenomenon that is typical of certain granulomatous diseases, but not as well defined in the literature for cancer (Kallas et al., 2010). Thus, it is important to consider calcitriol related hypercalcemia in malignancies with reduced PTH or PTHrP for proper treatment. Mirrakhimov A. E. (2015). Hypercalcemia of Malignancy: An Update on Pathogenesis and Management. North American journal of medical sciences, 7(11), 483 Anna Betlachin, MD, Sarah Sangnim Rhee Kim, MD, Rachael Oxman, MD, MPH, Calcitriol-Mediated Hypercalcemia in a Patient With Metastatic Gastrointestinal Stromal Tumor, Journal of the Endocrine Society, Volume 4, Issue Supplement_1, April-May 2020, Melissa Kallas, Francis Green, Martin Hewison, Christopher White, Gregory Kline, Rare Causes of Calcitriol-Mediated Hypercalcemia: A Case Report and Literature Review, The Journal of Clinical Endocrinology & Metabolism, Volume 95, Issue 7, 1 July 2010, Pages 3111.