This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Magnesium level in blood increases in: \nSelect and explain. \nA. Uncontrolled DM, B. Liver cirrhosis, C. Kidney failure, D. Chronic alcoholism', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The concentration of magnesium in serum is closely regulated within the range of 0.7–1 mmol/L (1.5–2 meq/L; 1.7–2.4 mg/dL), of which 30% is protein-bound and another 15% is loosely complexed to phosphate and other anions. One-half of the 25 g (1000 mmol) of total body magnesium is located in bone, only one-half of which is insoluble in the mineral phase. Almost all extraskeletal magnesium is present within cells, where the total concentration is 5 mM, 95% of which is bound to proteins and other macromolecules.\xa0\nBecause only 1% of body magnesium resides in the ECF, measurements of serum magnesium levels may not accurately reflect the level of total body magnesium stores.\nRegulation of serum magnesium concentrations is achieved mainly by control of renal magnesium reabsorption. Only 20% of filtered magnesium is reabsorbed in the proximal tubule, whereas 60% is reclaimed in the cTAL and another 5–10% in the DCT. Magnesium reabsorption in the cTAL occurs via a\xa0 paracellular route that requires both a lumen-positive potential, created by NaCl reabsorption and tight-junction proteins encoded by members of the Claudin gene family. Magnesium reabsorption in the cTAL is increased by PTH, but inhibited by hypercalcemia or hypermagnesemia, both of which activate the CaSR in this nephron segment.\n\xa0\nReference: :Harrison’s medicine page no\xa0 2916', 'role': 'assistant'}]