Endocrine Abstracts

A 73 year old man was admitted to the hospital with a multi-factorial fall. He was otherwise asymptomatic. Past medical history included stage 3 chronic kidney disease (CKD), ulcerative colitis, epidermolysis bullosa and mild cognitive impairment. Examination was unremarkable apart from unilateral leg swelling and deep venous thrombosis was excluded. Investigations showed incidental undetectable magnesium level and severe hypocalcaemia. Potassium level was normal, 25-hydroxy-vitamin D level was low and parathyroid level was appropriately raised. Electrocardiogram revealed normal sinus rhythm and high corrected QT interval. Treatment with intravenous magnesium and calcium rendered both electrolytes to normal. Medication review revealed omeprazole 20 mg once a day for more than 2 years for heartburn. He was not on diuretics and there was no suggestion of alcohol excess, diarrhoea or re-feeding syndrome. Hypomagnesaemia was attributed to the long term use of the omeprazole and the latter was replaced with ranitidine. He did not require further magnesium or calcium replacement and was commenced on cholecalciferol replacement for vitamin D deficiency. Proton pump inhibitor (PPI) induced hypomagnesaemia is rare but potentially serious complication of long term PPI use. Hypomagnesaemia is caused by reduced intestinal absorption of magnesium and seems to be a class effect seen with all PPIs. The severity of hypomagnesaemia is not linked to the dose of PPI but to the duration of use. The risk is higher in elderly population, females, people with concomitant diuretic use and with other co-morbidities especially diabetes or diarrhoea. Hypomagnesaemia can be associated with hypocalcaemia and hypokalaemia. Patients present with weakness, diarrhoea, leg cramps, paraesthesia, tetany, seizures and torsades de pointes. Physicians must recognise this potentially serious complication and switch patients from PPIs to H2-receptor blockers as the latter are not associated with abnormal magnesium absorption. Short term management involves replacement of magnesium, calcium and potassium. Cardiac monitoring in indicated especially in patients with prolonged QT interval. Risk benefit analysis should be carried out for patients in whom long term PPI therapy is being considered.