(11.08) Hyperparathyroidism in Pregnancy Resistant to Cinacalcet

Diagnosis of primary hyperparathyroidism (PHPT) is difficult during pregnancy owing to the non-specific nature of signs and symptoms. Pregnant women with a calcium level over 2.85 mmol/L (11.4 mg/dL) and prior pregnancy loss are at high risk of maternal complications and fetal loss. Around one-half of neonates born to mothers with untreated PHPT have hypocalcemia and tetany. Therefore, early diagnosis and management of PHPT is crucial to avoid complications.

Case(s) Description :

A 21-year-old G1P0 female with recurrent nephrolithiasis was admitted to the hospital for opioid detoxification, nausea and vomiting during her 4^th week of gestation. Initial blood work revealed an elevated calcium level of 13 mg/dL with hypophosphatemia (phosphorus 2.1 mg/dL), normal renal function, and hypercalciuria (415 mg/24 hr). Further evaluation showed an increased parathyroid hormone level of 410 pg/mL confirming the diagnosis of PHPT. The patient was started on intravenous (IV) fluids and the calcium levels decreased to 12 mg/dL. Neck ultrasound showed a hypoechoic nodule measuring 1.1x 0.6x 0.8 cm, suggestive of a right inferior parathyroid adenoma. Despite IV fluids, the patient was started on cinacalcet after discussing the risks and benefits of medical therapy versus surgical therapy in the first trimester. Calcium levels on cinacalcet were between 11.8-12.4 mg/dL with the ionized calcium ranging from 1.76-1.85 mmol/L. Given persistent hypercalcemia and failure to respond to medical therapy, she underwent parathyroidectomy during her 10^th week of gestation with normalization of PTH immediately post-operatively. The calcium level decreased to 10.1 mg/dL, phosphorus level increased to 2.7 mg/dL on post-operative day 1. Her symptoms improved and she was discharged from the hospital.

Discussion :

PHPT is rare during pregnancy given the diagnostic challenges due to the changes in calcium metabolism during pregnancy. Early diagnosis and appropriate treatment are extremely crucial to avoid maternal and fetal complications from hypercalcemia. Information on the appropriate management of pregnant women with PHPT is limited, and clinical knowledge in this area is restricted to isolated case reports and a few retrospective studies. Primary management is still conservative with forced diuresis. The definitive therapy is parathyroidectomy, preferably during the second trimester, but can be performed in the first trimester in patients with resistant hypercalcemia. The patient’s presentation is unique given the patient had persistent hypercalcemia resistant to conservative management thus requiring parathyroidectomy in the first trimester.