Primary hyperparathyroidism (PHPT) complicates 0.03% of pregnancies (1). It may be under-diagnosed as patients are often asymptomatic or have non-specific symptoms attributed to pregnancy. Normal physiological changes of pregnancy also reduce total serum calcium but not ionised or corrected calcium (1). PHPT can cause significant maternal and fetal complications (Table 1)(2).

A 26-year-old female primip was referred to our institution at 10-weeks-gestation with parathyroid hormone dependent hypercalcaemia and symptoms of fatigue, constipation and ostalgia. She had no significant personal or family medical history and only medication was multivitamins. Clinical examination revealed a small right thyroid mass. Baseline laboratory values are shown in Table 1. Ultrasonography demonstrated a viable pregnancy and an irregular hypoechoic 1.2x2.6x1.4cm right thyroid nodule (Figure 1) but did not identify a parathyroid adenoma.  Fine needle aspiration reported benign thyroid nodule histology. She was admitted and managed with hydration, frusemide and electrolyte and fetal monitoring. There was no improvement in hypercalcaemia and bilateral neck exploration and right hemi-thyroidectomy was performed. Calcium levels declined within hours post-operatively and normalised the following day. Operative findings and histology confirmed normal parathyroid glands. Right hemi-thyroid histology confirmed an intra-thyroidal parathyroid adenoma. Genetic testing for MEN-1 was negative and CDC73 is pending.  The patient continues to be monitored regularly and is progressing with her pregnancy without further complications.

Management of hypercalcaemia during pregnancy is limited as commonly used antiresorptive agents are contraindicated. Parathyroidectomy reduces complications and is recommended when corrected calcium exceeds 2.75mmol/L and ideally during the second trimester (3).  Two cases of ectopic parathyroid adenomas during pregnancy have been reported (4, 5). Pre-operative localisation is challenging. Ultrasonography is safe, however Sestamibi and 4DCT are limited by radiation exposure and MRI is less specific.  Bilateral neck exploration is considered the standard of care (4, 6).  This case highlights PHPT management during pregnancy, including maternal and fetal complications of hypercalcaemia, surgery indications, localising parathyroid adenomas during pregnancy and genetic testing and follow-up planning.

Table 1. Complications of hypercalcaemia in pregnancy (2)

Table 2. Baseline laboratory values

Figure 1. Thyroid ultrasonography