ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2017) 50 P194 | DOI: 10.1530/endoabs.50.P194

A well recognised but forgotten cause of undetectable Magnesium

Sajjad Ahmad1, Saeed Akbar2, Lindsey George2 & Marc Evans2

1University Hospital Llandough, Cardiff, UK; 2University Hospital Llandough, Cardiff, UK.

A 74 years old man prsented with gradually worsening confusion with associated jerky movements with background of well controlled type 2 Diabetes, CKD-3, IHD and previous duodenal ulcer. His was on Finasteride, Omeprazole, Mirtazapine, Tamsulocin, Metformin, Atorvastatin, Humulin I insulin. He was taking omeprazole for Duodenal ulcer since 1993.

On examination he had jerky movements of the arms suggestive of muscles spasms. Rest of the examination was unremarkable.

He was found to have Hypocalcemia of 1.63 mmol/L (NR 2.20–2.60) with inapproiately normal PTH of 6.6 pmol/L (NR 1.6–7.2). Serum potassium was normal. Furthur investigation into hypocalcemia revealed an undetectable Magnesium which was felt to be the likely cause of his Hypocalcemia. Serum Vitamin D level were low at 15 nmol/L ( NR >30). 24 hours urinary Magnesium was normal at 3.4 mmol (NR 2.4–6.5) which confirmed that there was no renal Magnesium loss.

ECG showed prolongation of the QTc (460 ms) with prolonged PR interval consistent with Hypomagnesemia.

He was treated with intravenous Magnesium and oral supplements and both Mg and Calcium were normalised. PPI was replaced with H2 blockers.

This gentleman had severe symptomatic hypomagnesaemia with undetectable Mg levels secondary to chronic PPI therapy.

PPIs impairs the active transport of magnesium in intestinal epithelial cells by inhibition of transient receptor potential melastatin 6(TRPM6) and TRPM7 channels. This is thought to be related to the changes in intestinal pH caused by Proton pump inhibitors. Hypocalcemia is a frequent associated finding as hypomagnesemia causes a degree of hypoparathyroidism by inhibiting the release of PTH from parathyroid gland as well as causing PTH resistance in bones.

Physicians need to have high index of suspicion to detect Hypomagnesaemia as it is not routinely checked, particularly patients on long term PPI therapy and Diuretics as advised by FDA and MHRA to avoid life threatening Cardiovascular and neurological sequelae.Unexplained hypocalcaemia and Hypokalemia particularly if refractory to treatment also warrants checking Magnesium levels.

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