Cinacalcet increases sensitivity of the calcium sensing-receptor, currently licenced for treatment of refractory secondary hyperparathyroidism in patients with end-stage renal disease. It decreases parathyroid hormone, calcium and phosphorus levels. There is no clinical data for the use of Cinacalcet in pregnancy. Hyperparathyroidism is rare during pregnancy, mainly presenting early, when surgery is safely performed. Here we report a patient presenting with a MEN1-associated parathyroid tumour in the third trimester, where surgery was delayed until post-partum.
A 27-year-old Caucasian lady with a positive family history for MEN1 presented with symptomatic hypercalcaemia at 33 weeks gestation. Parathyroid hormone level of 39.1 pmol/l (1.1-4.2 pmol/l) and adjusted calcium of 3.73 mmol/l (2.10-2.59 mmol/l) were elevated. Ultrasound revealed a right-sided enlarged parathyroid gland (30 mm×18 mm×8 mm).
Treatment with Cinacalcet was started and parathyroidectomy delayed until post-partum. Pre-term caesarean section at 34+3 weeks was performed; the child required 4 days respiratory support for pulmonary surfactant deficiency. Infantile corrected calcium at birth was 3.12 mmol/l but normalised within 3 days, still remaining stable.
Parathyroid gland biopsy confirmed parathyroid hyperplasia and the patient underwent complete parathyroidectomy with implantation of part of one gland as an autograph. Due to the background of familiar MEN1-mutation, pituitary and gastrointestinal neoplasia screening was performed but is presently negative.
Hyperparathyroidism during pregnancy can have devastating effects on both mother and foetus. At present there are no evidence-based parameters that reliably predict the outcome of hyperparathyroidism in pregnancy and optimal management remains uncertain. Most authors advocate parathyroidectomy during pregnancy as treatment of choice in second trimester, where safety of surgery in other trimesters is debated.
Treatment with Cinacalcet may be an effective approach in selected patients with hyperparathyroidism in the third trimester before surgery can be safely performed.