Background:  

PTH-dependent hypercalcaemia is rare in pregnancy with most cases being secondary to primary hyperparathyroidism (PHPT) with potentially significant maternofetal complications.(1,2)  

Methods:  

All cases of hypercalcaemia were identified using admission data coded for hypercalcaemia and pregnancy at a single tertiary centre in Sydney (January 2016-April 2026) and included if PTH-dependent. Data collected: demographics, timing of diagnosis, peak corrected calcium, management, PHPT-attributable complications and pregnancy outcomes. 

Results:  

Ten cases of PTH-dependent hypercalcaemia were identified (mean age 32.1±4.7 years). Diagnostic categories included: confirmed PHPT (n=7), likely familial hypocalciuric hypercalcaemia (n=1), likely PHPT (n=2). Eight had hypercalcaemia pre-pregnancy (mean 2.7mmol/L±0.08). Eight had peak pregnancy calcium>2.85mmol/L (mean 3.1mmol/L±0.3). Four were diagnosed pre-conception; six in third trimester. Seven were managed medically; three underwent parathyroidectomy during pregnancy (two in trimester 2, one at 32 weeks). All surgically managed patients remained significantly hypercalcaemic pre-surgery (>3.0mmol/L) despite medical management. All three achieved cure and delivered at term without complications. Three underwent postpartum parathyroidectomy, pathology confirming adenoma in two and parathyroid carcinoma in one. Medical therapies included intravenous fluids (n=10), calcitonin (n=6) and cinacalcet (n=2). 

All pregnancies resulted in live births. Complications among medically managed patients included pre-eclampsia (n=3), labour induction for hypercalcaemia (n=2), preterm birth (n=3) and neonatal intensive care admission (NICU) (n=4). Additional events included hypertension without pre-eclampsia (n=2) and nephrolithiasis outside pregnancy (n=4). One surgically managed patient had pre-existing hypertension. Maternal complications were seen at lower rate in those managed surgically compared to medically (X2(1, n=10)=4.3, p=0.04). No significant association was seen for NICU (X2(1, n=10)=2.9, p=0.09) or preterm birth (X2(1, n=10)=3.0, p=0.08).  

Conclusions:  

PTH-dependent hypercalcaemia in pregnancy is often diagnosed late due to symptom overlap and absent routine calcium screening. Medically managed PHPT was associated with maternal complications, supporting surgery when diagnosis is definitive. Findings were limited by retrospective design and small sample size.