Beyond Malignancy: Clinical Insights from Three Cases of Severe Hypercalcemia

Severe hypercalcemia is a life-threatening condition requiring immediate treatment alongside a systematic evaluation to identify the underlying cause. Although malignancy is a common etiology among hospitalized patients, alternative causes must be considered to guide targeted therapy, as illustrated in these cases. The first case involved a 31-year-old postpartum woman with corrected calcium levels of 14.5 mg/dL and suppressed PTH. Hypercalcemia resolved after tapering and temporary cessation of breastfeeding, consistent with lactation-associated hypercalcemia that is likely PTHrP-mediated. The second case describes a 30-year-old woman who presented with hypotension, hypercalcemia, hyperphosphatemia, and low PTH. A systematic evaluation revealed severe glucocorticoid deficiency consistent with primary adrenal insufficiency (Addison's disease). The final case featured a 47-year-old man with severe symptomatic hypercalcemia (18.5 mg/dL) and markedly elevated PTH. Imaging revealed a 3 cm parathyroid tumor. Selective parathyroidectomy produced a rapid intraoperative PTH decline, and pathology supported parathyroid adenoma rather than carcinoma. Together, these cases highlight that symptomatic severe hypercalcemia is a medical emergency warranting prompt clinical intervention, followed by an early PTH-based stratification to direct a focused, stepwise diagnostic workup and definitive management.