Primary hyperparathyroidism in pregnancy successfully treated with microwave ablation: a case report

Primary hyperparathyroidism (PHPT) during pregnancy is rare, with an estimated prevalence of <1% among pregnant women. While often asymptomatic, it may lead to serious maternal complications (nephrolithiasis, pancreatitis, preeclampsia) and adverse fetal outcomes (growth restriction, miscarriage, preterm delivery, stillbirth). Surgical parathyroidectomy in the second trimester remains the gold standard treatment, but may be unfeasible due to gestational age, contraindications, or patient refusal. In such situations, minimally invasive techniques such as microwave ablation (MWA) have emerged as potential alternatives, though their use in pregnancy is extremely rare, with only one case previously reported.

We report the case of a 38-year-old woman in her second trimester, with a history of multiple miscarriages and no living children, referred for hypercalcemia discovered on routine screening. Laboratory tests revealed corrected serum calcium of 11.54 mg/dL (85-105), elevated intact parathyroid hormone (iPTH) at 100.3 pg./mL (15-65), and marked hypercalciuria. Cervical ultrasound demonstrated a vascularized hypoechoic lesion posterior to the left thyroid lobe, consistent with a parathyroid adenoma, further confirmed by fine-needle aspiration with PTH washout (2075 pg./mL). After refusal of surgery, ultrasound-guided MWA was performed under local anesthesia with hydrodissection to protect adjacent structures.

Within 1 h, iPTH dropped to 16.8 pg./mL and serum calcium normalized to 10.0 mg/dL, remaining stable throughout pregnancy. Symptoms resolved within days. Obstetric monitoring confirmed healthy fetal development. At 38 weeks, the patient delivered a healthy infant by cesarean section. No maternal or fetal complications occurred.

This case represents only the second reported use of MWA for PHPT during pregnancy, demonstrating its feasibility, efficacy, and safety in a highly selected patient. MWA may provide a valuable minimally invasive alternative when surgery is contraindicated or refused, though further evidence is needed to define its role in this unique clinical context.