Endocrine Abstracts

Hyponatraemia in pregnancy can be precipitated by various factors, including drugs, fluid excess and oxytocin infusion. It is a common complication of pre-eclampsia toxaemia (PET), although concomitant syndrome of inappropriate ADH secretion (SIADH) in this context is rare. We present a case of SIADH leading to hyponatraemia in a PET patient. A 30 year-old primigravid woman with bipolar disorder and hypertension was admitted with pre-eclampsia at gestational week 28. Her medications included nifedipine, labetalol and quetiapine. At week 32, her sodium level dropped to 125 mmol/l. She appeared euvolaemic. Kidney function, glycaemic review and thyroid function were within normal range. She had a serum osmolality of 257 mosmol/kg, urine osmolality of 446 mosmol/kg and urine sodium of 32 mmol/l. The clinical and biochemical features were consistent with a diagnosis of SIADH. Despite fluid restriction, her serum sodium level did not improve. Four days later, an emergency Caesarean section was performed due to signs of foetal distress. Pre-operative serum sodium was 125 mmol/l, but it improved to 133 mmol/l on the first day post-operatively and she was discharged home with a serum sodium of 137 mmol/l. SIADH as a cause of hyponatraemia in PET is rare and only few reported cases are published. The mechanism of SIADH in pre-eclampsia is unclear, but it is thought that the reduced intravascular volume may stimulate excess ADH release. Hyponatraemia carries a prognostic significance and, if untreated, can lead to complications such as seizures in pregnant women and hyponatraemia in neonate. Severe hyponatraemia in this context can be challenging as clinically available drugs to treat hyponatraemia related to SIADH are contraindicated in pregnancy. However, the hyponatraemia usually resolves rapidly following childbirth. This case therefore serves as a reminder of a rare cause of hyponatraemia in PET.