7752 Navigating Hypercalcemia in Pregnancy: A Case Report

Abstract Disclosure: J. Gabbay: None. S. Steinmetz-Wood: None. Introduction: Primary hyperparathyroidism (PHPT) in pregnancy is rare but presents many diagnostic and therapeutic challenges. Prompt diagnosis and treatment are important due to associated maternal and fetal risks, however evaluation of urine calcium to differentiate from Familial Hypocalciuric Hypercalcemia (FHH) becomes less reliable due to physiologic changes in pregnancy, sestamibi scans. CT scans require radiation, parathyroidectomy introduces surgical risk, and medical alternatives like bisphosphonates can interfere with fetal skeletal development. Clinical Case: A 24-year-old woman who presented to the emergency room for progressive nausea and abdominal pain was found to be pregnant with elevated serum calculated calcium to 11.4 mg/dL (2.84 mmol/L). She had a history of renal stones, longstanding hypercalcemia of unknown etiology and a remote family history of parathyroid “issues”. Follow up laboratory work showed a PTH of 75.8 pg/ml (8.04 pmol/L) with an elevated 24-hour urine calcium and a low 25OH vitamin D. Given her history of kidney stones and overt symptoms it was our clinical judgement that this was not a case of FHH. She was started on IV fluids twice weekly. After an unrevealing neck ultrasound, an MRI neck showed a 7 mm lesion along the posterior aspect of the left thyroid suggestive of a parathyroid adenoma. Sestamibi scan was avoided due to the risks of radiation to the developing fetus. Given the presumptive diagnosis of parathyroid adenoma, the lack of response to aggressive hydration, and the maternal and fetal risks of hypercalcemia during pregnancy, parathyroidectomy was pursued in her second trimester. Intra-operative inspection and biopsy showed the lesion to be only a lymph node. She underwent 4-gland exploration and the left inferior parathyroid gland, which appeared abnormal and enlarged, was removed. The intra-operative PTH dropped only from 98 to 80 (10.4 to 8.5 pmol/L). She otherwise had an unremarkable hospital course and at discharge her calcium was normal with an undetectable PTH, which can be an expected finding in pregnancy. On follow up she was feeling well with sustained normocalcemia and low PTH levels. Given the age at which her hyperparathyroidism started, she was referred to genetics for further evaluation. Clinical Lessons/Conclusion: There were significant biochemical and radiological limitations in the management of this case. Normally an inappropriately normal PTH with elevated serum calcium and normal urine calcium/creatinine clearance ratio confirms the diagnosis of PHPT, however in pregnancy it should be noted that FHH could also present with normal or elevated urine calcium due to absorptive hypercalciuria in pregnancy. Additional clinical history and reasoning was needed for management as well as a skilled surgeon, where preoperative localization was limited and was not ultimately helpful. Presentation: 6/2/2024