Endocrine Abstracts

Introduction: Hypercalcemia in pregnancy is rare with limited treatment options, causing serious consequences to mother and foetus. Changes in calcium homeostasis in pregnancy can delay Primary hyperparathyroidism (PHPT) diagnosis.

Case Presentation: A 35-year-old pregnant woman was detected with hypercalcemia (3.06 mmol/l) at 14+1 weeks. Calcium was 2.83 mmol/l in March 2025, following a miscarriage. She was otherwise asymptomatic. She was commenced on intravenous fluids. Biochemistry revealed: PTH 14.5 (1.6-6.9 pmol/l), phosphate 0.88 (0.8-1.5 mmol/l) and Vit-D 75 (>50 nmol/l). Thyroid and renal function tests normal. 24-h urinary calcium excretion was 22.08 (2.50-7.50 mmol/24hs) whereas, urine calcium creatinine ratio (UCCR) was 0.023, diagnostic of PHPT. Imaging was limited to Ultrasound Neck and KUB. No parathyroid adenoma or renal calculi. She was referred to the regional tertiary centre where she underwent parathyroid exploration with left superior parathyroidectomy at 16+4 weeks, in view of severe hypercalcemia. Intraoperatively PTH dropped (310 to 22 pmol/l) with Calcium returning to normal (2.3mmol/l) post-operatively indicating cured PHPT. Histopathology revealed parathyroid lipoadenoma.

Discussion: Normal changes to Calcium homeostasis in pregnancy such as reduction PTH may render PHPT diagnosis challenging. The high transplacental transfer of calcium (mediated by PTH-rP), although may confer some protection against hypercalcemia, can cause diagnostic delays by masking hypercalcemia. Hypercalcemia increases risks of miscarriage, preeclampsia, and neonatal hypocalcaemia. Definitive management is surgical, ideally in second trimester to minimize risks of miscarriage and preterm labour. Conservative measures may be considered in mild cases (Calcium <2.85 mmol/l). Multidisciplinary coordination between endocrinology, endocrine surgeons and obstetrics is essential for optimal outcomes.

Conclusion: UCCR is not reliable in distinguishing PHPT from FHH, and where FHH is a strong possibility, genetic testing should be arranged. In pregnancy, PHPT is a biochemical diagnosis. Imaging is for guiding surgical approach and not for diagnostic purposes.