Potassium and Magnesium Turnover in Magnesium Deficiency

Magnesium deficiency. Etiology and clinical spectrum

Magnesium deficiency may complicate many diseases. The causes include the following: inadequate intake during starvation or increased requirement during early childhood, pregnancy, or lactation; excessive losses of magnesium as a result of malabsorption from the gastrointestinal tract or from the kidneys during use of diuretics; and to a combination of the two, as in alcoholism. Most often the etiological factors have been operative for a month or more. Acute hypomagnesemia can occur without previous Mg deficiency after epinephrine, cold stress and stress of serious injury or extensive surgery. The clinical manifestations depend on the age of the patient and may begin insidiously or with dramatic suddenness, or there may be no overt symptoms or signs. The manifestations can be divided into the following categories: totally non-specific symptoms and signs ascribable to the primary disease; neuromuscular hyperactivity including tremor, myoclonic jerks, convulsions, Chvostek sign, Trousseau sign (rarely), spontaneous carpopedal spasm (rarely), ataxia, nystagmus and dysphagia; psychiatric disturbances from apathy and coma to some of all facets of delirium; cardiac arrhythmias including ventricular fibrillation and sudden death; hypocalcemia which is responsive only to Mg therapy; and hypokalemia which is not easily nor completely corrected without Mg therapy. The diversity of etiologies and the multiplicity of manifestations result in confusion and controversy. The documentation of normal renal function is absolutely necessary for maximum doses. The order of magnitude of dose is 1.0 meq Mg/kg on day 1, and 0.3 to 0.5 mEq/kg per day for 3 to 5 days. In emergencies such as convulsions or ventricular arrhythmias, a bolus injection of 1.0 gm (8.1 meq) of MgSO4 is indicated. Therapy of Mg deficiency in the presence of renal insufficiency requires smaller doses and frequent monitoring. Complete repletion occurs slowly.

Magnesium metabolism in Huntington's chorea

Human magnesium deficiency states are known to be associated with tremor, choreiform and athetoid movements, delirium and convulsions. In order to assess a recent report of altered magnesium metabolism in Huntington's chorea, 6 patients with the disease have been studied with complete balance studies, exchangeable magnesium studies, erythrocyte and ultrafiltrable magnesiums and 2 patients with spinal fluid magnesium determinations. Balance studies failed to suggest any abnormalities. Exchangeable magnesium28 values were within normal ranges (4.3 ± 0.7 mEq./Kg. at 24 hrs.), as were erythrocyte magnesium determinations (5.29 ± 0.42 mEq./L.). Ultrafiltrable magnesiums were normal and the 2 spinal fluids evaluated had normal magnesium values. These results are not compatible with the hypothesis of altered magnesium metabolism in Huntington's chorea.