(4.07) Hypercalcemia Due to the Ectopic Production of Intact Parathyroid Hormone from High-Grade Endometrial Adenocarcinoma

Thursday, May 9, 2024

12:25 PM – 12:40 PM CDT

Location: ePoster Showcase, Empire Ballroom Foyer, Level 2

Submitter(s)

Andrew Jung, DO

Endocrinology fellow
Rochester Regional Health
Rochester, New York, United States

Introduction : Malignancy-associated hypercalcemia is relatively common and is linked to various etiologies. However, ectopic production of intact parathyroid hormone (PTH) from malignancy is a rare condition, accounting for less than 1% of malignancy-associated hypercalcemia cases. Here, we present a case of severe hypercalcemia attributed to the ectopic secretion of PTH by endometrial carcinoma.

Case(s) Description :

A 73-year-old female presented at the emergency department with altered mental status, prompting an evaluation that revealed hypercalcemia. She had no prior history or family history of hypercalcemia. Initial laboratory tests indicated corrected calcium at 14.7 mg/dL (8.3-10.6), ionized calcium at 8.2 mg/dL (4.5-5.3), magnesium at 2.4 mg/dL (1.6-2.6), phosphorus at 3 mg/dL (2.4-5.1), alkaline phosphatase at 100 U/L (46-116), vitamin D 25-hydroxy at 84 ng/mL (≥20), and an elevated intact PTH at 385 pg/mL (18-80).

Additional initial studies included PTH-related protein at 1.1 pmol/L (≤4.2) and unremarkable serum protein electrophoresis. After experiencing vague abdominal pain, the patient underwent a CT abdomen and pelvis with IV contrast, revealing a constellation of findings indicative of uterine malignancy with metastasis involving the abdominopelvic lymph nodes and liver. A biopsy of the liver lesions confirmed metastatic high-grade carcinoma, with staining negative for PTH.

Attention was then redirected to evaluate for primary hyperparathyroidism. A four-dimensional parathyroid CT with and without contrast showed no evidence of a parathyroid adenoma. A subsequent endometrial biopsy revealed high-grade adenocarcinoma with focal squamous differentiation, and PTH staining was positive. Treatment for hypercalcemia involved calcitonin, zoledronic acid, and denosumab. The patient was ultimately scheduled for the initiation of targeted chemotherapy for endometrial cancer.

Discussion : This case highlights the uncommon etiology of malignancy-associated hypercalcemia and illustrates that the site of metastasis may not exhibit the same staining characteristics as the primary source. Ectopic PTH secretion from malignancy is a rare phenomenon. To our knowledge, there have been only four reported cases of hypercalcemia caused by ectopic parathyroid hormone secretion associated with endometrial cancer.