A 27-year-old alcoholic man presents with decreased appetite, mild generalized weakness, intermittent mild abdominal pain, perioral numbness, and some cramping of his hands and feet. His physical examination is initially normal. His laboratory returns with a sodium level of 140 mEq/L, potassium 4.0 mEq/L, calcium 6.9 mg/dL, albumin 3.5 g/dL, magnesium 0.7 mg/dL, and phosphorus 2.0 mg/dL. You go back to the patient and find that he has both a positive Trousseau and a positive Chvostek sign. Which of the following is the most likely cause of the hypocalcemia?
Correct Answer: Decreased end-organ response to parathyroid hormone because of hypomagnesemia
Description: One of the commonest causes of hypocalcemia is impaired parathormone (PTH) production. Hypomagnesemia causes decreased production of PTH as well as decreased end- organ response to the hormone. Alcohol causes increased urinary losses of magnesium which then leads to the mentioned effects on PTH and ultimately to hypocalcemia. Poor dietary intake and osteoporosis do not lead to hypocalcemia unless the patient has vitamin D deficiency. Routine calcium levels are not accurate in the setting of a low albumin. To estimate the true calcium level, one may add 0.8 mg/dL to the observed calcium level for every 1 g/dL reduction in the albumin level (from 4 used as normal). In this case, the albumin is not far from 4 and hence the calculation would change the low calcium level very little. An ionized calcium level is consistent and accurate regardless of the albumin level.While pancreatitis can cause hypocalcemia, this patient's presentation does not suggest the condition.
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