SUN-509 A Challenging Case of Symptomatic Primary Hyperparathyroidism during Pregnancy Treated with Cinacalcet

Primary hyperparathyroidism (PHPT) during pregnancy is rare. Hypercalcemia (HCa) may be undetected due to hypoalbuminemia and increased active transport of calcium via the placenta. Undiagnosed HCa may present with life threatening maternal hypercalcemic crisis and fetal hypocalcemia. In patients with moderate and severe HCa, parathyroidectomy (PTx) is recommended during the second trimester. Cinacalcet is approved for treatment of secondary hyperparathyroidism in patients with ESRD, HCa due to parathyroid carcinoma, and in patients with severe HCa due to PHPT unable to undergo PTx. However, cinacalcet use in pregnancy is limited to a few case reports. We present a case of PHPT presenting with severe HCa and cardiomyopathy where PTx was contraindicated due to risk of cardiac decompensation. To our knowledge this is the first case of cinacalcet use in PHPT where therapeutic doses were well tolerated resulting in a safe delivery without maternal and fetal complications. A 38 year old female at 25 weeks gestation (gravida 7, para 4) presented from an outside hospital for treatment of pyelonephritis and new onset cardiomyopathy with reduced ejection fraction of 20%. The patient had a history of preeclampsia but denied a personal or family history of nephrolithiasis and calcium abnormalities. Present medication included a prenatal multivitamin. Physical exam revealed tachycardia, hypotension and no palpable neck mass. Laboratory evaluation revealed a corrected calcium 13.8 (8.7-10.7mg/dL), ionized calcium (iCa) 1.7 (0.95-1.32 mmol/L), phosphate 1.7 (2.5-4.6 mg/dL), magnesium 1.5 (1.6-2.7 mg/dL), creatinine 0.83 mg/dL. Treatment with normal saline 0.9 % was started with IV furosemide to prevent fluid overload. Further evaluation showed an elevated intact parathyroid hormone 383 (8-85 pg/mL), elevated 1,25 dihydroxyvitamin D 147 (18-78 pg/mL), normal parathyroid hormone related peptide 14 (14-27 pg/mL), fractional excretion of calcium of 1.7%, and fractional excretion of phosphate of 25% confirming the diagnosis of PHPT. A neck ultrasound showed a 2 cm left thyroid nodule; FNA biopsy confirmed a parathyroid adenoma. Evaluation for MEN 1 was negative. Due to severe cardiomyopathy, the patient was deemed a poor surgical candidate. Treatment with cinacalcet 30 mg daily was started and slowly titrated to 90 mg twice daily. On discharge, iCa had normalized to 1.26. The patient was readmitted to the hospital four days prior to delivery for discontinuation of cinacalcet and prevention of fetal parathyroid gland suppression. The patient delivered a healthy male at 37 weeks of gestation without hypocalcemia. Treatment of PHPT during pregnancy is challenging especially in those patients who are unable to undergo PTx. Cinacalcet may be a safe option to prevent maternal and fetal complications of HCa in patients with PHPT. Further studies are needed to evaluate the safety of cinacalcet in pregnancy.