Endocrine Abstracts

Case history: A 32 female was referred to a tertiary maternity unit due to hypercalcaemia and a diagnosis of primary hyperparathyroidism (PHPT). She had learning difficulties, 2 previous C-sections and was a smoker. She presented 5 years earlier to her local hospital with abdominal and leg pains, nausea, constipation and fatigue. She had undergone 2 parathyroidectomies but remained hypercalcaemic and had been managed medically with Cinacalcet when she conceived an unplanned pregnancy.

Investigations: At the initial diagnosis of PHPT:

• Corrected calcium 3.05 mmol/l

• PTH 8.5 pmol/L

• Vitamin D 15.4 nmol/l

• Normal prolactin and metanephrines

• 24-hour calcium was 4.2 mmol/24hr (2.5–7.5) felt to be consistent with PHPT

• Normal renal ultrasound scan

• Parathyroid localization with ultrasound and Mibi scan showed no adenoma

Results and treatment: Neck exploration removed 2 inferior parathyroid glands felt to be hyperplastic but histologically normal. After surgery, she remained hypercalcaemic and symptomatic. Repeat urinary calcium levels were lower but there were concerns about the collection and Vitamin D deficiency. Imaging again showed no evidence of an adenoma. Repeat parathyroidectomy removed a right superior parathyroid adenoma but the hypercalcaemia persisted and Cinacalcet was started. At the antenatal clinic at 20 weeks gestation, corrected calcium-3.05 mmol/l, PTH 5.0 pmol/l, Vitamin D 24.4 nmol/l and Hammersmith spot Urinary Calcium: Creatinine ratio 0.004. The hypercalcaemia in pregnancy was managed conservatively with good hydration, requiring a couple of admissions for intravenous fluids due to vomiting. The pregnancy was otherwise uncomplicated. At 37 weeks gestation, calcium levels appeared to be rising and she underwent an elective C-Section delivering a male infant weighing 2.4 kg. In light of the maternal PHPT, the paediatric team was alerted to the risk of hypocalcaemia. However, at 12 days of age corrected calcium-3.46 mmol/l, PTH 3.4 pmol/l and Vitamin D 28.7 nmol/l.

Conclusions and points for discussion: The baby’s results suggest a diagnosis of Familial Hypocalciuric Hypercalcaemia (FHH), rather than PHPT. Genetic analysis is awaited.

1. FHH is an important differential diagnosis of PHPT and should be excluded. It has a benign course and does not require surgical management.

2. FHH should be reconsidered if hypercalcaemia persists after surgery.

3. Hypercalcemia among family members suggests the diagnosis of FHH.

4. Vitamin D deficiency may worsen hypocalciuria and hyperparathyroidism making the differentiation between PHPT and FHH challenging.

5. Urine calcium: creatinine ratio <0.01 is accepted as a differentiating feature of FHH but there is overlap with higher levels and genetic testing should be performed to prevent patients from undergoing inappropriate surgery due to misdiagnosis.