Abstract: SA-PO527
Abnormally Normal? A Patient with Hypercalcemia of Malignancy Presenting with Normal PTH
Session Information
- Acid-Base, Calcium, Potassium, and Magnesium Disorders: Clinical
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Andaya, Amelito Manuel Logronio, Piedmont Athens Regional Internal Medicine Residency Program, Athens, Georgia, United States
- Andaya, Amelito Miguel Logronio, University of Santo Tomas Faculty of Medicine and Surgery, Manila, Metro Manila, Philippines
Group or Team Name
- Piedmont Athens Regional GME.
Introduction
In malignancy-related hypercalcemia, serum PTH are usually suppressed with noted elevation in PTHrP. We present a case of hypercalcemia of malignancy due to suspected lung cancer with normal PTH levels.
Case Description
A 73 year old man with multiple substance use including tobacco and alcohol, hypothyroidism, and hypertension presented with a several-day history of confusion and eventually unresponsiveness. He was hypotensive on presentation that responded to normal saline bolus. On exam, he was somnolent, tachycardic, had severely dry oral mucosa, impaired skin turgor, and generalized abdominal tenderness. Pertinent workup showed hypercalcemia at >18, hypernatremia at 154, elevated creatinine at 2.18 and BUN at 66. Ionized calcium was high at 1.81. On further investigation, PTH was normal at 24.30 but PTHrP was elevated at 85. Chest CT scan with contrast demonstrated multiple pulmonary nodules, right hilar and mediastinal adenopathy, lymphangitic carcinomatosis, and bilateral small pleural effusions. Aggressive IV hydration with IV lactated ringers at 150 mL/hr was done. IV zoledronic acid and calcitonin were started. Serum calcium then improved and stabilized to 10.7 however patient’s altered sensorium persisted, eventually becoming more agitated. He was then assessed to have metastatic lung cancer and was transitioned to hospice after extensive discussion with the patient and his family.
Discussion
Excessive secretion of PTHrP is said to be the most common cause of hypercalcemia of malignancy. This patient presented with normal PTH levels of 24.30 which would have otherwise led the diagnostic trail to other non-malignant causes of hypercalcemia. Although there is no standard, any PTH greater than 20 pg/mL is considered unsuppressed. In addition, another interesting development was the persistence of the patient’s mentation despite eventual successful lowering of the serum calcium. This was hypothesized to be likely secondary to other factors including possible CNS metastasis, hypothyroidism, or undiagnosed dementia. Hence, with the findings of this case, clinicians should not always expect suppression of PTH and at the same time, must be careful in interpreting parameters of improvement in hypercalcemia especially in patients with multiple risk factors.