Familial hypocalciuric hypercalcaemia (FHH) is an autosomal dominant condition characterised by chronic mild hypercalcaemia in association with hypocalciuria, hypermagnesaemia, and normal to mildly elevated parathyroid hormone (PTH) levels. It is caused by a mutation in the calcium sensing receptor (CASR) gene and tends to have familial association. The measurement of a 24-hour urinary calcium-to-creatinine clearance ratio (CCCR) can be used to help distinguish FHH, with confirmatory genetic testing available. Typically, patients remain asymptomatic through their lifetime and do not develop significant complications. There is no specific treatment for FHH.
During pregnancy, the most common cause of hypercalcaemia is primary hyperparathyroidism (PHPT). It is important to recognise and identify the presence of PHPT as it can be associated with miscarriage, intrauterine growth restriction, pre-eclampsia, pancreatitis and hypercalcaemic crisis. Definitive treatment of PHPT is parathyroidectomy, which is preferentially performed in the second trimester.
The assessment of hypercalcaemia during pregnancy can be complicated by physiological changes. Dilutional hypoalbuminaemia leads to reduced total calcium levels, and ionised calcium is therefore the preferred measurement in pregnancy. Hypercalciuria is also seen in pregnancy as a result of increased intestinal calcium absorption (absorptive hypercalciuria), which makes the interpretation of urinary CCCR difficult.
There are currently few case reports of FHH in pregnancy in the literature. My poster will focus on differentiating FHH and PHPT in pregnancy, and examine a case series of pregnancies in Queensland women with FHH (who have had confirmatory CASR gene testing) to investigate maternal and neonatal outcomes and compare these to women with PHPT.