SAT250 A Case Of Hypercalcemia In Pregnancy - A Diagnostic And Management Challenge

Disclosure: W. Cheng: None. Y. Kuan: None. Hypercalcemia in pregnancy is rare and poses significant diagnostic and management challenges especially in a low resource setting. Although primary hyperparathyroidism (PHPT) is the main cause, physiological changes in calcium homeostasis make it difficult to distinguish from familial hypocalciuric hypercalcemia (FHH) unless genetic testing is done. Furthermore uncertainty exists on the safety of pharmacotherapy for hypercalcemia in pregnancy which if untreated, can be detrimental to both mother and child. Described herein a 17 year-old primigravida who presented at 32 weeks of gestation for asthma exacerbation precipitated by COVID-19 infection. She was incidentally found to have PTH-dependent hypercalcemia with albumin-corrected calcium 3.42 mmol/L [2.10-2.55] associated with raised intact parathyroid hormone (iPTH) 15 pmol/L [1.6 - 6.0] and deficient serum 25OH Vitamin D at 19.95 nmol/L [50-125]. She was given IV saline of 3-3.5L/day but to no avail as her serum calcium was persistently above 3 mmol/L with an episode of premature uterine contraction. Calcitonin was given in short courses and withheld once albumin-corrected calcium dropped below 3 mmol/L but rebound within three days. As bisphosphonates is contraindicated in pregnancy, we introduced cinacalcet, up to 75mg/day after discussion with the patient and her family. Meanwhile, investigations were done to ascertain underlying cause. Fractional urine calcium excretion ranged from 0.0068 (spot urine sample) to 0.0568 (24-hour urine sample). Ultrasound neck did not reveal enlarged parathyroid glands or an adenoma. Sestamibi scan was contraindicated in pregnancy. Genetic testing for FHH was too costly but all her first-degree relatives tested to have normocalcemia. Blood pressure remained normal throughout pregnancy. She was discharged with cinacalcet at calcium level of 2.7 mmol/L. However she defaulted follow-up and medications and presented at 36 weeks of gestation for preterm labour. She gave birth to a healthy, 2.46kg baby girl. The baby had neonatal jaundice but normal calcium level. Postpartum, the patient was asymptomatic despite persistent hypercalcemia 3.12 - 3.15nmol/L. As she was non-compliant to cinacalcet it was stopped and serum calcium did not worsen. Sestamibi scan is planned after she stops breastfeeding and a reassessment of the urine calcium once vitamin D is adequately replenished. She refused exploratory parathyroidectomy. She continued to be followed up at the endocrine clinic while her baby at primary care. Contraception is advised untill definitive diagnosis and treatment of hypercalcemia. This case illustrates the challenges in managing hypercalcemia in pregnancy and difficulty in distinguishing PHPT vs FHH without genetic testing. Presentation: Saturday, June 17, 2023