Endocrine Abstracts

A 68-year-old lady presented to the medical assessment unit with history of muscle cramps involving both hands and legs of 5 days duration. She also gave a history of diarrhoea of 2 weeks duration. Her background medical history includes hypertension, hypercholesterolemia and dyspepsia for which she was taking Irbesartan/hydrochlorothiazide combination tablets, simvastatin and omeprazole.

General physical examination revealed positive Chovstek’s and Trausseau’s signs. Her investigation results confirmed low adjusted serum calcium level of 1.22 mmol/l (normal range 2.15–2.6 mmol/l) along with low serum magnesium level of 0.14 mmol/l. Her serum 25 hydroxy-vitamin D level was also on the lower side at 14 ng/ml and PTH level was marginally raised at 8.3 pmol/l. ECG showed normal sinus rhythm with borderline QT duration at 450 ms.

She was treated with 10 mls 10% calcium gluconate in 100 mls 5% dextrose infusion over 5 min followed by 100 mls 10% calcium gluconate in 900 mls 5% dextrose infusion over 24 h. She also received 16 mmol of magnesium sulphate infusion in 1 l 5% dextrose over 24 h. Her symptoms resolved with this treatment and both her serum calcium and magnesium levels returned to normal at 2.28 and 0.75 mol/l respectively. However, she continued to have diarrhoea with an average frequency of 3-4 times per day. Her stool culture result was reported negative for bacterial pathogens but further investigation with flexible sigmoidoscopy confirmed the diagnosis of colitis for which she was started on a course of oral steroid therapy.

Despite on-going diarrhoea, the patient was discharged from hospital without any oral calcium or magnesium supplement. She also continued to take both irbesartan/hydrochlorothiazide and omeprazole tablets which further increased her risk for recurrent hypomagnesaemia. Not surprisingly the patient was readmitted 2 weeks later with recurrence of neuromuscular symptoms along with profoundly low serum calcium and magnesium levels of 1.4 and 0.15 mmol/l respectively. She was once again treated with both calcium and magnesium infusion until her serum levels returned to normal. She was also maintained on oral magnesium glycerol phosphate at a dose of 24 mmol/ day in three divided doses. Her hydrochlorothiazide tablet was stopped to reduce renal magnesium wasting and her omeprazole tablet was replaced with ranitidine. She has remained asymptomatic since and both her serum calcium and magnesium levels have stayed normal.

Conclusion: This case highlights the importance of identifying and correcting modifiable risk factors for recurrent hypomagnesaemia such as drugs as well as the need for prescribing maintenance oral magnesium supplementation in patients with ongoing magnesium loss.