A 55-year-old homeless man comes to the emergency department with muscle cramps and perioral numbness. The patient appears malnourished and says that he has consumed a lot of alcohol recently. His past medical history is significant for chronic-recurrent abdominal pain for which he was advised to quit drinking alcohol. His temperature is 36.7 C (98 F), blood pressure is 110/65 mm Hg, pulse is 80/min, and respirations are 18/min. Examination shows a regular heart rate and clear lung fields. The abdomen is soft without significant tenderness. There are normoactive bowel sounds. Laboratory studies are as follows: Which of the following is the most probable cause of the hypocalcemia observed in this patient?

Question

A 55-year-old homeless man comes to the emergency department with muscle cramps and perioral numbness.  The patient appears malnourished and says that he has consumed a lot of alcohol recently.  His past medical history is significant for chronic-recurrent abdominal pain for which he was advised to quit drinking alcohol.  His temperature is 36.7 C (98 F), blood pressure is 110/65 mm Hg, pulse is 80/min, and respirations are 18/min.  Examination shows a regular heart rate and clear lung fields.  The abdomen is soft without significant tenderness.  There are normoactive bowel sounds.  Laboratory studies are as follows:  Which of the following is the most probable cause of the hypocalcemia observed in this patient?

Quizplus · Accepted Answer

11ec25c8_d3c0_3aa7_bc81_4f794f454077_MD0003_00 This patient has symptomatic hypocalcemia associated with significant hypomagnesemia and hypophosphatemia. Hypomagnesemia is very common in hospitalized alcoholics and can cause hypocalcemia by inducing resistance to parathyroid hormone (PTH) as well as by decreasing PTH secretion. The cause of hypomagnesemia in alcoholics is multifactorial, and may include urinary losses, malnutrition, acute pancreatitis, and diarrhea. This patient has additional features of malnutrition/malabsorption including anemia and mild hypoalbuminemia. Hypocalcemia due to hypomagnesemia is typically refractory to treatment with calcium unless magnesium is replaced as well. Although PTH levels increase rapidly after magnesium replacement, hypocalcemia takes longer to improve because PTH resistance persists despite improvement in magnesium levels. Despite PTH deficiency, phosphorus levels are normal or low in magnesium deficiency; this is possibly due to intracellular phosphorus depletion. (Choice A) Extracellular deposition of calcium can lead to hypocalcemia. This may occur in patients with hyperphosphatemia, osteoblastic bone metastasis, and acute pancreatitis. This patient has chronic abdominal pain but no specific features of acute pancreatitis. (Choice B) About 50% of circulating calcium is protein bound, predominantly to albumin. Consequently, serum total calcium varies with albumin concentration. Interpretation of serum calcium levels requires correcting for the serum albumin level (serum calcium concentration falls by 0.8 mg/dL for every 1 gm/L decrease in albumin). This patient's serum calcium is low even after correcting for the mild hypoalbuminemia. (Choice D) Hypophosphatemia generally coexists with hypomagnesemia in alcoholic patients. Decreased gastrointestinal absorption and increased renal loss of phosphate are causes of hypophosphatemia in alcoholism. Hypophosphatemia itself does not cause hypocalcemia. (Choice E) Resistance to PTH (pseudohypoparathyroidism) may result in hypocalcemia with high PTH and high phosphate levels. This condition is very rare and is usually associated with characteristic facial features (ie, Albright hereditary osteodystrophy). Educational objective: Hypomagnesemia is an important cause of hypocalcemia, particularly in alcoholics. Hypomagnesemia causes decreased release of parathyroid hormone (PTH) and PTH resistance. Hypoparathyroidism induced by low magnesium is not associated with elevated phosphorus levels (as seen with other causes of hypoparathyroidism). References: Hypocalcaemia and chronic alcohol intoxication: transient hypoparathyroidism secondary to magnesium deficiency (http://www.ncbi.nlm.nih.gov/pubmed/8777856)

A 55-Year-Old Homeless Man Comes to the Emergency Department with Muscle