An Uncommon Case of Lactational Hypercalcemia With Diagnostic and Therapeutic Challenges

A 35-year-old female patient was referred to General Medicine by Obstetrics for high calcium levels identified in routine postpartum lab tests. She had persistent vomiting throughout pregnancy and had been managed with antiemetics without lasting relief. On initial work-up, her parathyroid hormone (PTH) was found to be suppressed, suggesting a non-PTH-related etiology. Comprehensive investigations, including bone profile, erythrocyte sedimentation rate (ESR), myeloma screening, imaging (CT, PET), and respiratory evaluation, excluded malignancy, sarcoidosis, and other common causes. Despite a trial of intravenous (IV) fluids, low-dose steroids, and calcium management, the patient's condition persisted, necessitating referral to specialized centers. After exhaustive consultations, ectopic PTH secretion was identified as the likely cause of the elevated calcium levels. Given the challenges related to lactation and breastfeeding, the management required coordination between obstetrics, endocrinology, and maternity services to ultimately manage hypercalcemia. This case highlights the diagnostic complexity and the importance of an interdisciplinary approach in managing rare conditions like lactational hypercalcemia and ectopic PTH secretion in the postpartum period.