Hypocalcemia

Published on 02/03/2015 by admin

Filed under Endocrinology, Diabetes and Metabolism

Last modified 02/03/2015

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CHAPTER 16

Hypocalcemia

1. Define hypocalcemia.

2. How are serum calcium and serum albumin levels related?

3. How is the total serum calcium corrected for a low serum albumin level?

4. What is the most common cause of low total serum calcium?

5. What factors other than albumin influence the levels of serum ionized calcium?

6. How is serum calcium regulated?

7. What steps in vitamin D metabolism may influence serum calcium levels?

8. What are the major causes of hypocalcemia?

The multiple organ and hormonal regulatory systems involved in calcium homeostasis create the potential for multiple causes of hypocalcemia. The etiology of hypocalcemia must be considered in relation to the level of serum albumin, the secretion of PTH, and the presence or absence of hyperphosphatemia. Initially, hypocalcemia may be approached by a search for failure in one or more of these systems. The systems primarily involved are the parathyroid glands, bone, kidney, and liver; the following list shows the clinical entities followed by their mechanisms:

image Hypoparathyroidism: decreased PTH production

image Hypomagnesemia: decreased PTH release, responsiveness, and action

image Citrate toxicity from massive blood transfusion: complexing of calcium with citrate

image Pseudohypoparathyroidism: PTH ineffective at target organ

image Liver disease: decreased albumin production, decreased 25-hydroxyvitamin D production, drugs that stimulate 25-hydroxyvitamin D metabolism

image Renal disease: renal calcium leak, decreased 1,25-dihydroxyvitamin D production, elevated serum phosphate (Po4) from decreased Po4 clearance; drugs that increase renal clearance of calcium

image Bone disease: drugs suppressing bone resorption; “hungry bone syndrome”—recovery from hyperparathyroidism or hyperthyroidism

image Phosphate load: endogenous—tumor lysis syndrome, hemolysis, and rhabdomyolysis; exogenous—phosphate-containing enemas, laxatives, and phosphorus burns

image Pancreatitis: sequestration of calcium in the pancreas; other

image Toxic shock syndrome, other critical illness: decreased PTH production or PTH resistance

9. What physical signs suggest hypocalcemia?