Endocrine Abstracts

Gitelman’s syndrome (GS) is a rare autosomal recessive renal tubular disorder caused by defects of thiazide sensitive Na-Cl co-transporter due to mutations of the SLC12A3 gene.

We report a case of a 23-year-old woman, who presented with excessive tiredness in her second pregnancy. She had a past history of hypokalaemia in a previous pregnancy (attributed to ‘vomiting’), which required multiple admissions for i.v. potassium replacement despite oral potassium supplementation. Her serum potassium returned to normal following delivery.

In her second pregnancy she reported no history of vomiting, diarrhoea, laxative or diuretic misuse, or liquorice ingestion. She was normotensive with no Cushingoid features.

Investigations revealed a severe hypokalemic metabolic alkalosis with serum potassium 2.5 mmol/l (3.5–5.5) and bicarbonate 42 mmol/l (22–30). Further investigations revealed; serum magnesium 0.60 mmol/l (0.7–1.0), corrected calcium 2.55 mmol/l (2.15–2.60), and phosphate 1.08 mmol/l (0.80–1.50). Urinary potassium excretion was 89 mmol/24 h (40–120). Urinary calcium excretion was low at 2.12 mmol/24 h (2.5–7.5) and cortisol excretion normal at 64 mmol/24 h (50–350). Ambulant serum renin (38.3 ng/ml per h (1.5–5.7)) and aldosterone (2939 pmol/l (140–850)) were significantly elevated. A urine screen for diuretics was negative. She was treated with magnesium and potassium supplements but despite this required frequent hospital admissions for i.v. potassium replacement. Both pregnancies resulted in uneventful obstetric and neonatal outcomes.

Subsequent maternal DNA analysis detected one mutation of the SLC12A3 gene.

This case illustrates that i) GS may be unmasked during pregnancy and ii) in GS, increased tubular loss of potassium may result in severe pregnancy-related hypokalaemia. GS should be considered as a cause of pregnancy related hypokalaemia where on-going renal losses are apparent and no other cause is evident. Pre-pregnancy counselling should be offered to women with GS who should be monitored closely.