MON-158 Primary Hyperparathyroidism in Pregnancy: Parathyroidectomy in the Third Trimester

Abstract Disclosure: M.P. Acharya: None. S. Sapna: None. B. Cunningham: None. I. Gabriely: None. A. Gabriely: None. Primary hyperparathyroidism (PHPT) is characterized by hypercalcemia and elevated or non-suppressible parathyroid hormone (PTH) levels. The clinical presentation ranges from asymptomatic to symptoms or signs of hypercalcemia, as well as renal and/or skeletal manifestations. In pregnancy, hypercalcemia presents heightened risks for both maternal and fetal health, necessitating early recognition and prompt intervention to mitigate morbidity and mortality.Case PresentationA 28-year-old female at 27 weeks and 5 days of gestation presented to the ED with bilateral flank pain. Imaging via CT of the abdomen revealed ureteropelvic calculi and bilateral hydronephrosis. Laboratory findings were notable for corrected calcium of 13 mg/dL, ionized calcium of 1.55 mmol/L, 25-hydroxyvitamin D of 4.3 ng/mL, magnesium of 1.1 mg/dL, and PTH of 130 pg/mL. A 24-hour urine calcium collection confirmed hypercalciuria. The patient was diagnosed with PHPT four years prior; however, she was lost to follow-up. She reported no history of nephrolithiasis, fractures, or medications associated with hypercalcemia (e.g., lithium or hydrochlorothiazide).Initial management with intravenous fluids failed to significantly reduce calcium levels. Given the relative contraindications of most pharmacologic treatments for hypercalcemia during pregnancy, parathyroidectomy (PTX) was recommended. She underwent partial PTX and lithotripsy with stent placement simultaneously. Intraoperative findings revealed a right upper parathyroid adenoma. Postoperative PTH levels confirmed successful excision.Discussion: Young age, marked hypercalcemia, and nephrolithiasis are indications for PTX in PHPT. Managing this condition during pregnancy requires balancing maternal and fetal safety with the timing of surgical intervention. PTX is ideally performed in the second trimester, a period associated with reduced risks of preterm labor and miscarriage. Surgery during the third trimester is generally avoided due to risks of preterm delivery. Untreated hypercalcemia in pregnancy carries maternal risks, including worsening nephrolithiasis and renal insufficiency, while fetal risks include intrauterine growth restriction, neonatal hypocalcemia, and stillbirth due to transplacental calcium transfer. In this case, surgery was necessary, as the risks of untreated hypercalcemia outweighed surgical complications. This underscores the need for individualized management based on a careful risk-benefit assessment.ConclusionThis case highlights the importance of timely diagnosis and management of PHPT in reproductive-aged women, particularly before pregnancy. In pregnant women, a multidisciplinary approach involving endocrinology, obstetrics, and surgery is essential to determine the safest course of action. Presentation: Monday, July 14, 2025